I don't know if it's really an honest question, but I'll answer honestly. You're wrong about 99% of games being about incest, not the majority even, in last updates frontpage for example there are 30 games on page 1, just 5 of them are incest-related. Let's see the full released games content on site - All games available: 15737; with incest: 2263 games, meaning roughly 15%. So you're argumentation is intrinsically wrong, concerning the question itself: It's a matter of preference, as yours to not like it, there is the possibility of other people liking things that you don't actually like. Me for example, I don't particularly like incest myself over other genres that are much more appealing to me, but disregarding that, I don't have siblings, my actual mother is much beyond my preferred age range for even being a consideration, like 20 years beyond, my aunts are on that range or even older, I don't have female cousins either, considering all that and how they don't look particularly attractive to me, makes me wonder how it would be to have a experience that I don't have in my current life. Cause games for me are a form of escapism, you know, alternate reality/experiences. What in actuality don't make sense to me is play a game that is exactly like my current reality with possibilities or interactions that I would most probably have/will have. Could I, maybe, invest more time in real life than playing a game about relationships that I could have in real life, and even, I don't know, find a real longtime partner, find a better job, have real friends over emulating that on a computer? But again, is matter of opinion.