It's hard to create gameplay tension when you have female mc opposite to a female romance interest.
As opposed to the glorious gameplay tension of every woman throwing her pussy at your beta simp lame ass. Women can grind dead-end jobs to buy flowers and chocolates just as well, or what kind of "gameplay" did you have in mind?
You can't breed, giving one sided pleasure is a given
Tribadism. Oviposition too since OP did not exclude furries.
once you get to licking each other stage of the relationship you have nowhere to go
Licking fingers, licking tongues, licking pussy, licking anus, strap-on, strap-on anal, fisting, threesome/orgy/marriage...
You can have 1 be a psychopath and mistreat the other with drugs, tattoos and violence, but that has limited appeal.
You can have the other be into that stuff which adds financial pressures and maintaining public appearances to the mix. Honestly other than impregnation there is little men can do at the level of detail most games show that women can't.
What kinda activities do 2 women, who are less into sex than men, do when they have free time? Something boring I guess.
Why would they be less into sex? Sure you can pull out some poll statistics but this is fiction not real life. Men aren't exactly portrayed accurately either starting with the forearm-sized schlong and continuing with them fucking their step-sister, step-mother, landlady and step-dog all in a day's work.
Play as a broke student during spring break. Or an intern who has the hots for her female boss. Or a professional dominatrix. Or a succubus in an all girls Christian boarding school. Or an amazon warrior renowned for laying dragons.
I can sorta understand where the difference in popularity comes from between realporn and games though: porn you just leave playing while masturbating/warming up with a partner, you just look at hot women. It's easy to imagine them doing it "for" you if not "with" you. In games you need to interact, to an extent you need to
be the woman not just oogle her tits. That's harder to market to "strictly hetero" guys so your potential audience is much smaller.