Quote Originally Posted by ADaisyChain
Or because they know it's what their boyfriend wants and they are made happy by making him happy. ((this concept makes me ill! to each their own))

I'm sure there are lots of other reasons as well, but I could see lots of self-respecting girls using this one.

If your boyfriend treats you like a whore, there's a strong possibility he thinks of you as no better then one.
Thats not true, loving couples engage in sadomasochism all the time. It doesn't make them cruel people, its just a sexual deviancy.