I think there are quite a few games that would work for straight women, as in, most characters to go after are male. The mentioned Insexsity for example has definitely more male characters to interact with than females, and you can also chose what you want to do mostly. And I know quite a lot more games where the lesbian part is small or non-existant.
Its not really about the lack of males in female protagonist games (at least the ones I know), its more about the feeling that those games are still made for male players.
And after rechecking the female protagonist tagged games, it shows that they are all made by males, for males. The female MC works as its really in an overwhelming percentage a setup for a male fantasy of corrupting them, there isnt really a "live a normal life and meet people as female game". Most games do give choices though, you as a player can chose in which situation you run the character into, or at least sometimes chose with whom the corruption part takes place.
Interesting that its such a strong theme in both industries, japanese and western. Even the Lesson of Passion series has female characters, but they also mostly have male players in mind, and again a lot of them play with the corruption.
Guess to have a game that would really be suited for females, it would need a female developer. Funny enough, the only one I know off thats doing adult games does some of the more depraved content, not that I mind.