Take a look at the world and decide for yourself. How do you think we are doing with the Christ Principle, given the nuclear threats, the starving millions, the thousand million poor? We are indeed fortunate that, for the love of humanity, the man, the Son of Man, has graced us with his presence. Furthermore, the primary reason for his physical return is to lead his group, the Spiritual Hierarchy of Masters, back into the world.
This question, I think, arises from the mistaken idea that an Avatar (in this case the Christ) is some kind of abstract Principle which might embody itself in many individuals simultaneously. Many people see the Christ in this sense, separating the man ― Maitreya ― from the Christ Principle which he embodies, and looking for a multiple manifestation of the Christ. The Christ Principle does indeed manifest through millions today, but this is only one of the three ways in which Maitreya promised to appear ― on mental, astral and dense physical levels. My submission is that all three forms of his manifestation have taken place.