Cleanliness isn't an issue. Girls have things that get much dirtier, in case you haven't noticed. And, uh, foreskins have worked for the vast majority of humans, and their ##s haven't fallen off (most of the time).
You know, that's an impressive array of sense organs and nerves down there. Circumcision does decrease sensitivity and pleasure. If you doubt me, feel free to google it.
For most males, there's no medically sound reason to circumcise. And if there is a medically sound reason to do so, it's not, as NB found out, impossible to circumcise later in life. Later-in-life circumcisions don't entail the same loss of sensitivity, but the circumcisee does know what he's missing.