You might be right. I have no problem with the incest scenario (on the contrary) and it seems many others think the same. I still wanted to point out this could be Asamis idea without any of that.
Im also not just gonna rattle off kinks. Requesting stuff others aren't into has a tendency to devolve into a flame war, from my experience. And while the game is reasonably vanilla right now, I don't mind that either.
That said I have seen a few games out there proudly proclaiming "no close relations" in their description. Yet containing a mother-like and sister-like figure for the MC with custom definable relationship types. Eg a default of "landlord" which a player could change to eg "mother" anyway. This made me think there might be reasons for devs to stay away from or hide incest content.