I second what
recreation said about the female MC tending to become a massive slut being a problem for some female MC games, but for me the problem for female MC games is the problem where the player is activly working against the will of the PC, when she sin't a slut character she doesn't want to be having sex with anything with two (or sometimes more) legs and that really wrecks a game for me.
There is also the fact that as a guy who writes i can tell you for a fact that even if your good at writing from the female perspective(which i'm not particularly) you are always aware that your writing from a less personal perspective, sure you can step into her shoes but walking a mile in them is somewhat tougher than if i were to do the same with a man, it's the heels that i can't get used to, but seriously it's harder for a man to write a good female character in the first person than it would be to write a male character. This applies mainly to the first person, i have no problem writing a female character in the third person but climbing into a female characters head for a whole game is taxing in a way that doing so for a male character isn't, as such having the MC be male in a hypothetical game i would write would be far more in my comfort zone, i'd be more self assured in the writing being decent and i think a lot of writers prefer to do the same for that reason.
There is also the old "for men by men" argument, porn is dominated by guys or more specifically it's aimed at a male audience, women watch plenty of porn but in my experience they are far less likely to ever admit to or talk about it, as such porn is more often aimed at men as they are the "obvious" audience, therefore the MC would be more relatable to the target audience if he where male.
As for Futa, Futa is niche, there is unlikely ever to be the mass market for futa that there is for straight, lesbian and gay porn, while i get that it has a "best of both worlds" appeal it also presents problems in terms of the audience, i personally have no problem with futa x women but futa x man doesn't work for me at all, IMO futa for an MC would be a can of worms because you'd have to be careful of finding "the line" that you'd have to tread for a whole game or risk alienating a portion of your fan base.
There is also an element of "if it ain't ..." if a writer were to find a modicum of success with a male MC game, especially through a pay per update model a la patreon ect. there is a risk that by saying "the next game will have a female protagonist/Futa protagonist" they would alienate there audience to such a degree that the revenue stream would dry up very quickly and if your a dev who was able to go full time on he back of the previous game suddenly the 9 to 5 is looming again, effectively shutting you down, or at least putting you into checkmate with people expecting development times and quality on a level with your previous work, something you'd never be able to do while working full time.
TL: DR
- men may relate with men easier
- Futa is Niche
- It's harder(in first person) for a man to write a female MC
- change is inherently risky for an established Dev, why change from a "winning" formula?
- the market is smaller for fem MC games due to playerbase being a greater proportion of men to women
- Fem MC games don't always appeal to women, especially when written in certain ways.
Also "portagoist" is my word of the day(it's still better than i could do outside of my native language to be fair)