[DanaC]

Or because filmmakers assume that for the threat to be credible it has to come from a male source. Facing and beating a male super villain grants status to the hero - besting a woman is just to be expected because she's only a woman. It doesn't grant status - if the hero has to really struggle to overcome the male villain it increases his status further - but if he has to really struggle to overcome the female villain it actively reduces his status.

I remember spending time on some gaming and general geek forums and some of the disdain and even anger at the idea of female super heroes kicking about with male heroes and winning fights was amazing. It always baffled me, because they were willing to suspend disbelief at the notion of a man flying, turning into a mutant, or being given superpowers by a spider bite - but the idea that a woman could beat a man in a fight was a stretch too far. Why? Maybe because they wanted to imagine themselves in that narrative and a powerful woman was not what they wanted in there with them. Or because a woman's presence in that fantasy on an even footing with male characters devalued it by reducing the status of any male character who fought her.

Woman are allowed to be heroes and villains as long as the primary weapons they employ are sex and cunning.