Unfortunately it is so inprinted in our culture and, especially, by the media. We are tought from a very early age that women are supposed to be submissive, weak and only there to please men, and men are tought to be tough, strong and violent (mostly subconcious, of course), and thus of course, violence happens.
It doesn't help that we live in a society that teaches women "not to be raped" rather than men "not to rape".