In addition to the “traditional” reasons, your mom may have had you circumcised for at least one or more of the reasons below that she won't tell you (and don't embarrass both of you by asking!):
She wanted you to get blow jobs. Much more likely if you're clean, dry and don't smell bad. Circumcised boys often have to look up the word “smegma” in a dictionary. They have no idea what it is because they never produce any.
She knew that girls like circumcision. It's clean (see above), and it's sexy. The sight of a bare glans (head of the penis) is a major turn on for most women.
She knows or knew another woman who did not have her son circumcised at birth and later regretted it.
She once had a bad experience with an uncircumcised man, or knew another woman who did.
If this post attracts a number of anti-circumcision post, as these kinds of posts often do, ask yourself, this question, based on my own experience what rings true, and what doesn't?