Na I know that, it isn't good for business. But when I still went on the forums I remember Fenoxo, Savin, all the writers who stayed, they all didn't just say, "No incest, the money will disappear if we do it.". They got weirdly defensive about it and talked about it like it was the worst fetish imaginable and ruins the game by having it.
Like I vaguely remember Savin's game, CoC2, having backstory/lore on one of the salamander-girls descendants from CoC talking about how their great-grandmother realized she was being groomed and was almost "raped" by her father and then they go into just saying how disgusting incest is. It was either in the game or on a forum post but I do remember that being the canon end to the open-ended salamander quest in CoC.
Nothing wrong with no incest in the game from a financial standpoint, but you can't throw stones in a glass house and call it icky when the games are like 99% populated by furry futas.