Right, but is that because players have come to expect incest content or because they assume every female character who's friendly with the MC has to be lewdable or feel a certain entitlement to? Maybe something else?
I could be way off and this could be confirmation bias, but when I play a game with a non-lewdable sister, then I catch myself thinking that I wish she were an LI, not because she's the sister, but because she's a great character. I'm trying my best not to be condescending, but maybe other players aren't that conscious about why they feel drawn to this character and link it to the incest kink instead of it being about her characterization and ingrained bond they already have to the MC?