oh my god...have you read my answer yet??? hadith and sunnah, god told you to obey that as well, which are the words and actions of muhammed. there are probably plenty more reasons as well, ill list a few:
if you are not circumcised you are more likely to have problems down below, eg, my cousin who is not muslim, hes a christian had to get circumcised at the age of 31, by doctors because he had problems and infections down below so they sorted it out that way. i know this happens to very few people, but it does still happen, so its better to be on the safe side than get infections. also, as i said, it did not hurt me at all. i disagree with the female circumcision, and i have not heard that ever apart from here, and no girls in my family who are muslim or muslims i know have had it done, so it must be a cultural thing in specific countries, but it sure is not religious.