There is this common and fairly widely accepted argument that the reason why so many women are submissive/have rape fantasies is that women are slut-shamed, and so are often sexually inhibited. So if they are the "unwilling", passive recipient of sex, if sex happens to them, then they get to experience pleasure without having to directly express desire. And that can be liberating. Now obviously this doesn't mean that actual sexual assault is good, this dynamic should still happen between trusting partners that respect each other. But female submissive fantasies are often fueled by this underlying experience, and in BDSM, this is considered pretty normal afaik. It can be played out even in fairly vanilla relationships to various degrees, as men are expected to be the more proactive party by default.

Now the thing is, I think all of this applies to submissive men too. Men don't get slut shamed, but are worried of being creeps/not deserving of sex, and so many men can have heavy inhibitions as well. Submissive men are allegedly the second most common kink category after submissive women, I definitely think they are more common than people assume (and are probably growing in numbers but that's just my subjective impression).

But regardless, I think it's very difficult for men to be "passive recipients" of sex with women, in big part because the pursuing/initiation is largely on men, meaning they have to be kind of impressive in the woman's eyes to begin with. And that's the very thing where shame comes for a lot of men. Imagine if sexually inhibited, shyer women who let's say had some bad experiences when they were young had to go through dating men like that, in such a proactive, go-getter manner by default. Sure, maybe AFTER learning to be like that, men can eventually afford to lay back and get dominated by a woman who is then comfortable with it from time to time. But that's essentially backwards. Like men have to heal their shame before women are comfortable looking at it, and therefore, men cannot really be helped like submissive women.

Then there is the issue that the idea of sexual stuff happening to men is seen as unrealistic, porn-brained, selfish or even outright sexist. Women tend to dislike men wanting to be the passive recipient of sex, and they see that as entitlement. Well, women live in a world where men are "too much" for them in general, so it is sort of understandable. But I think this is a big reason why there are so few dominant women, and why even those rare ones tend to complain about men wanting a "kink dispenser". Not to say that men cannot be inappropriate or overzealous, but I think it's clear why this sort of stuff is difficult.

On the other hand, women like cool and nice things, and so if they can genuinely appreciate a more assertive male partner who can straight up help a more inhibited/shy girl by being assertive and caring at the same time, then women in theory should be able to have a "wait a moment, why only men can be like that, we are very cool too" sort of revelation. I do believe that women have the potential to be more okay with being an assertive lover taking on somewhat of a "helper" role - some may disagree with me on that but I think the difficulty of that is largely societal.

I think a big part of the issue is simply that women don't really take men's shame seriously, and that all circles back to women lacking empathy and understanding for the male side of heterosexual dating, how that feels, and how it can suck. This is one good reason why empathy matters - it could improve femdom and make humanity more versatile in how we can engage with each other, make us more complete as a species.