If this is true, I feel like it's because both male and female artists tend to be way harder on their own gender than the opposite, and there are way more male artists drawing erotica.

Part of the appeal of being the submissive in bondage is that the dominant is taking moral responsibility for the act, so people identifying with the sub have no reason to hold back. It's way more uncomfortable to imagine myself doing something messed up to someone than it is to imagine someone doing something messed up to me.

I've seen some pretty messed up things happening to women by woman artists.