But I tell you the truth, it is to your advantage that I go away; for if I do not go away, the Helper will not come to you; but if I go, I will send Him to you.Jesus being on Earth was a wonderful thing. But because He was human, there were limitations to Him. In particular, He could only be in one place at one time, and that limited the number of people He could directly influence at a time.
However, the Holy Spirit does not have physical limitations. He can be anywhere and everywhere, helping anyone who wants it simultaneously. Jesus opened the door to the Father, but it is the Spirit who keeps pushing us along the path to be more like Him.