I think
gunderson summed up a good lot of it, not to infer that what I say they would agree with =)
I put a good amount of thought into this as, full disclosure, shortly after finding this style in gaming I really wanted to make one and am up to my neck in the process but back to the point. I wasn't totally set on doing "incest" exactly, but a game and it seemed as if the most popular were of the incest variety. No coincidence and not unlike many others Big Brother was the first game I played. I had zero issue with the topic but struck me as odd that so many people played them and it didn't seem probable that everyone that did would have a thing for their own family. My best guess was simply that the charects or archetypes of incest games were fairly formulaic, that may have more to do with knockoffs than the topic but the result is mostly the same. Mom, experienced, voluptuous, nurturing. Older sis, hot, fit, little stuck up. Younger sis, cute, sexy youthful bod, innocent. If someone had a thing for any one of those types they'd be in one of these games. If someone liked variety, whelp, there ya go. Getting into creating the challenge was to take that, more or less, and try to figure out a motive other than "MC has a dick."
To go even further I talked to a shrink, told him about these games I had stumbled on and that I was going to make one and that it was based on incest. Hand to God I actually did and this is what he said "That sounds like a pretty good idea, incest is pretty popular these days." He was speaking in an entertainment sense, not that he had a bunch of clients participating just to clarify =) And he went on to say rather nonchalantly that it was just because it's taboo. Didn't go into some long Freudian explanation, just that it's taboo.
And I didn't realize it until I was a good chunk into my game but it's kind of crazy that as a topic it still has the stigma that it has, to the point that content deemed as "incest" is banned on some sites when Game of Thrones ... do I need to even finish that?
And my last little tid-bit of prattle about it is that I was a good chunk into working on mine that I realized, the first novel I ever read was loaned to me by a neighbor girl when I was somewhere between 9 and maybe 11. She was reading it and there was a pretty girl on the cover and I asked her what it was about. She gave me the basics along the lines of this woman's husband dies and she has three children and goes to live with her parents but can't let her Dad know about her kids so she and her Mom hide them away and lock them in the attic. Flowers in the Attic is was called by V.C. Andrews. I asked her if I could borrow it when she was done and she was like "I'm not sure it has some dirty stuff." which of course only made me want to read it more. So she said I could but she'd have to ask my Mom first. Apparently my Mom said something like "If he want's to read then yea! Let him borrow it!" I'm not sure if she told my Mom and I didn't realize till reading it that the naughty bits were about a brother and sister but my larger point is that the book was released in 1979 and was sold anywhere and everywhere including the frikkin grocery store. And VC Andrews became HUGELY popular, and the follow up books, Petals on the Wind, If There Be Thorns, Seeds of Yesterday, right next to Harlequin Romance novels at the grocery store. She went on to write a slew more similar, and even after she died her publisher hired ghost writers to keep writing books in her name.
Which leads me to conclude, there's a whole lot of stuff that seems more "perverted" that really ain't, not saying in practice, but as a topic or theme or element. But it seems to me that when it comes to the internet, the general public assumes or asserts a darker, more sinister, perverted spin on it. HBO, grocery store, and still Shakespeare would have been kicked off of Patreon. Figure that one out.