People aren't convicted unless they're proven guilty. We don't have cameras watching everyone 24/7, so it is possible for a man to commit rape, and yet for it not to be possible to prove it. This false symmetry would therefore lead to many innocent women falsely stigmatized as unchaste; historically, even though a woman is not to blame for being raped, that still meant she wasn't a virgin, and she was treated as "damaged goods" accordingly.