[buran77]

Anecdotally, every person I know to have a circumcision performed on them had it because "it was normal" in the society, not for any religious belief. Not wanting to stand out is a good enough reason for many. In some places an uncircumcised penis is (was?) considered "gross" or "abnormal" and many parents just want to avoid that for their child.

[tomrod]

Right. This is one of the few instances where how the social norm evolved can be determined.