>>28
In the case of HIV, it's because the foreskin has a high concentration of cells targeted by the virus. Hygiene has nothing to do with it.
Honestly, I don't think it's a big deal if you're cut or uncut. If you're uncut, it's more work keeping the first mate clean, but hey, it's nothing you can't take care of, and sex feels better for you. (How much better is unclear, so I won't try to judge that.)
If you're cut, your penis is less sensitive from being exposed (how much less is also unclear), but hey, sex still feels really really good, and it's less work for you in the shower. Plus you can regrow your foreskin if you really want to:
http://foreskinrestorationchat.info/completeguide.htm
Now, female circumcision's a different story. That's just fucking wrong.