There are a myriad of less obvious reasons, other truths that Jesus wanted to hammer home, which He could not do if He were still with us. Perhaps the most obvious is
The reality of the Eucharist
Think about it; if the physical Jesus was here, many would be tempted to say, “Why bother with this Bread and Wine when we have the real person right here.” They/we would not have paid attention to Jesus’ statement: I am the bread that came down from heaven. [Jn 6:41] 
Nor His mandate: Amen, amen, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you do not have life within you. [Jn 6:53]
Nor His promises: Whoever eats my flesh and drinks my blood has eternal life, and I will raise him on the last day. For my flesh is true food, and my blood is true drink. Whoever eats my flesh and drinks my blood remains in me and I in him. Just as the living Father sent me and I have life because of the Father, so also the one who feeds on me will have life because of me. This is the bread that came down from heaven. Unlike your ancestors who ate and still died, whoever eats this bread will live forever. [Jn 6:54-58]
Do you really think we would be carrying out His directive: Do this in memory of me [Lk 22:19; 1Cor 11:24] if we had “the real thing” right here on earth, particularly these days when He would probably be viewed 24/7 on His own channel, streaming live on your cell phone.
- We needed to be weaned off the created real and fed the adult food of the Divine Real.
- We needed to grok the fact that Jesus is indeed not only spiritually still with us, but now physically present with us…and
- We need to understand that He is no longer limited by His personal physical body to one location, but He is simultaneously PHYSICALLY PRESENT ALL OVER THE WORLD in the perfect form for simultaneously feeding us physically and spiritually.
And, while this could have been done if He stayed among us, how much faster did we “get it” after He rose into heaven. For immediately after Pentecost, we witness this understanding already realized in the daily life of the earliest Christian community: They devoted themselves to the teaching of the apostles and to the communal life, to the breaking of the bread and to the prayers.[Acts 2:42]
Thus, today, through His ordained priests, we can say: “This, indeed, is my body that is for you. This cup is, indeed, the new covenant in my blood. Do this in remembrance of me.” Indeed, as often as you eat this bread and drink the cup, you proclaim the death of the Lord until he comes. [1Cor 11:24-26, amended]
The reality of the Holy Spirit
The Spirit was definitely active in the disciples during the ministry of Jesus as exemplified when He summoned the Twelve and gave them power and authority over all demons and to cure diseases, and he sent them to proclaim the kingdom of God and to heal [the sick] [Lk 9:1-2].
But, for the most part, they were still frightened, and Jesus predicted that “All of you will be scandalized in me, for it is written: ‘I will strike the shepherd, and the sheep will be dispersed.’”[Mt 26:31], nor, even after his resurrection, did they fully understand: When they saw him, they worshiped, but they doubted [Mt 28:17] and even asked: “Lord, are you at this time going to restore the kingdom to Israel?” [Acts 1:6].
Jesus knew the Apostles had not absorbed and understood all that He had revealed to them; I have told you this while I am with you. The Advocate, the holy Spirit that the Father will send in my name—he will teach you everything and remind you of all that [I] told you.[Jn 14:25-26] He said this in reference to the Spirit that those who came to believe in him were to receive. There was, of course, no Spirit yet, because Jesus had not yet been glorified. [Jn 7:39]
Indeed He admits that He had “much more to tell you, but you cannot bear it now. But when he comes, the Spirit of truth, he will guide you to all truth.” [Jn 16:12-13] After His resurrection, He explicitly gave His Spirit to them:And when he had said this, he breathed on them and said to them, “Receive the holy Spirit. [Jn 20: 22] But it seems still a limited outpouring…explicitly for the forgiveness and retention of sin.
While the Spirit could have been outpoured fully as He was on Pentecost if Jesus had not ascended, but remained here on earth, we would have never come to rely on the Spirit as Jesus wished us to do. And they were all filled with the holy Spirit and began to speak in different tongues, as the Spirit enabled them to proclaim. [Acts 2:4] While these tongues given the Apostles on Pentecost were very practical, i.e. they we the languages of those who gathered outside and heard the word of God in their native speech, Peter, in his explanation to the crowd what has happened, refers to the prophecy of Joel: I will pour out a portion of my spirit upon all flesh. Your sons and your daughters shall prophesy, your young men shall see visions, your old men shall dream dreams. [Acts 2:17; Jl 3:1-5], where glossolalia, or the prophesying or “praying in tongues” was foretold.
More to the point, the Spirit is our defense lawyer before the world; instead of He being our “mouthpiece,” we are to be His as He proclaims the Truth of God in the face of opposition: When they hand you over, do not worry about how you are to speak or what you are to say. You will be given at that moment what you are to say. For it will not be you who speak but the Spirit of your Father speaking through you. [Mt 10:19-20]
Throughout the Book of Acts, we witness the action of the Spirit in our midst, bringing more and more believers into the community, organizing the community and allocating particular jobs within the Church, infusing the Apostles and even Peter’s shadow with the power to heal, passing judgment through them on evil doers in their midst, demonstrating the changes in “the Law” of what is clean and unclean, both in food and in affiliation, stopping Paul from going some places and beckoning him to come to others, even saving shiploads from drowning and shaking off vipers with immunity.
In particular, we might not have come to understand that the Spirit’s imprimatur is even greater than the Church’s, guiding the sensus fidelium, the sense of faith of the entire people of God within the Churchwith infallible Truth: “The entire body of the faithful, anointed as they are by the Holy One, cannot err in matters of belief. They manifest this special property by means of the whole peoples’ supernatural discernment in matters of faith when “from the Bishops down to the last of the lay faithful” they show universal agreement in matters of faith and morals. That discernment in matters of faith is aroused and sustained by the Spirit of truth.” Lumen Gentium, 12.
It would be very sad if, because Jesus was still physically present on the earth, we would be frightened to exercise our universal and individual charisms, those special gifts of the Holy Spirit give to each Baptized individual to be used for the benefit of the entire Church, the entire Body of Christ. We might have been tempted to be lax in their exercise, sloughing off our responsibilities as the Father’s adopted sons and daughters with the excuse that “He here; let Him do it.”
We are held to a high standard of performance, not only in quality but in actual exercise of our gifts. Lord, grant us each the grace to know our gifts, to appreciate our gifts and to use them to take Your message with us, wherever we go.
The reality of the Church
Under the guidance of the Spirit, the Church devoted themselves to the teaching of the apostles and to the communal life, to the breaking of the bread and to the prayers…they would sell their property and possessions and divide them among all according to each one’s need. Every day they devoted themselves to meeting together in the temple area and to breaking bread in their homes. They ate their meals with exultation and sincerity of heart, praising God and enjoying favor with all the people. And every day the Lord added to their number those who were being saved. [Acts 2:42, 45-47]
While Jesus was among them after His resurrection and before His Ascension, He was the one who nurtured and taught them, whose personal charisma kept them together. Now that He has Ascended and the Spirit has taken charge, Christ is in their midst because they are two or three gathered together and (He is) there in the midst of them [Mt 18:20], and they are functioning as a community.
As the Church grew, the Apostles appointed deacons and they all went out from Jerusalem to preach, teach and baptize. And Peter was taught by the Spirit of the universal nature of the call of Christ [Acts 10] and that no one is to be excluded. And Jesus calls Paul to carry His message to the Gentiles…and the word spreads throughout Asia Minor, Africa, Greece and on to Rome.
The Church is no longer simply where Jesus is humanly present, but becomes world wide in its presence. The Church recognizes leaders and a focal home, first in Jerusalem, and then in Rome. While all followers take up the mandate to teach all nations, there is a unified structure, a shared Good News, a growing tradition, a learning curve of those things bound and those things loosed…and all this under the guidance of the Spirit while carrying Jesus with them in the Word, in the breaking of the Bread, in the common faith, in the love for one another.
When Jesus was present, even then and, perhaps especially then, there were squabbles about who is the greatest in the kingdom, who will sit at Jesus right and left hand, and they became indignant….Jesus summoned them and said, “You know that the rulers of the Gentiles lord it over them, and the great ones make their authority over them felt. But it shall not be so among you. Rather, whoever wishes to be great among you shall be your servant; whoever wishes to be first among you shall be your slave. [Mt 20:24-27]
But this didn’t take hold until after Jesus ascended, had left them, and the Spirit comes; He will teach you everything and remind you of all that [I] told you.[Jn 14:26]. And his disciples remembered that he had said this, and they came to believe the scripture and the word Jesus had spoken:[Jn 2:22] the Son of Man did not come to be served but to serve and to give his life as a ransom for many. [Mt 20:28]…and they finally get it. That’s what the Church is, we finally got it…but it took His leaving and the Spirit coming to make that happen.
 Scripture texts in this work are taken from the New American Bible, revised edition © 2010, 1991, 1986, 1970 Confraternity of Christian Doctrine, Washington, D.C. and are used by permission of the copyright owner. All Rights Reserved. No part of the New American Bible may be reproduced in any form without permission in writing from the copyright owner.
 See Paul on the proper use of glossolalia: 1 Cor 14:6-19