Most of the doctors that do it today, do it for reasons of cleanliness and maybe God wanted it done for that reason but that does not explain why He would not have done it right the first time. The primary reason was to make the Jewish nation a separate and obedient people. As Christians, baptism serves the same purpose and we are to circumsize our hearts, the Israelites were also told to circumsize their hearts. Remember also that it is of course only the males that have to do this. If it were another part of the body, there would be no clear difference as to male and female.
Sin is suposed to enter into humanity through the seed of man.
What other bloody rite could have been imagined that would have sent fear into the hearts of men and the proof of obedience except a symbol of his manhood. What we are trying to do here is become one with the love and unity that God would expect of us. For some, this is not possible for it takes denying ourselves and coming into that humbleness that we also We as Christians are to be circumcized in the heart and what must happen before we are truly in the fellowship of God. To judge and condemn our brothers and sisters because they do not agree with the narrow minded bias of others is to fall into condemnation ourselves. It is a tragic circumstance.