I just think that such thing as "objective facts" exists. But i'm not sure about statistics overall (how much popularity each fetish can have), so i can't really say something about it. It's really hard to persuade large group of people. And incest fans is really large group in many forums i know. Unlike niche fetishes. And incest, as i think, is larger than something like netorare as fetish. So many different variations, and how can you include all that in game. There is a people, who only like mother as romance option. Someone else only like bro+sister, sis+sis, or daddy+daughter, or aunt, or mother-in-law, or zillion other types. NTR is largely known only as two common types - netori (usually sweeter one) and netorare (darker one, that can largely include rape, drugs etc).
I have something like incest fetish, but it's not as strong as you might think. I have large amount of stronger fetishes that i like better. For example, netori. And mature\married women. Even if they're not "my mother" type, i don't really care. Incest can be boring after awhile. So, you can say that i'm the one of this people who "ask about non-incest route at an incest game" too. I like variety and diversity in all that, stories, body types, faces, large amount of women to choose etc. Not just harem and infinite group sex.
And i can imagine some people hating incest, harem, tentacles, cuz i've seen such comments. Even there. Or just zillion of "another one of this incest games?"
