I have a pet hypothesis that, on average, those into step porn are more likely not have grown up with a sibling of the gender they fancy. I reckon those of us who did are more likely to repelled by anything alluding to incest.
People who grew up with ACTUAL hot step siblings notwithstanding.
Yeah, coincidentally the majority of “teens” fucking each other seem like they have the best scenes, the girls are into it. Probably because they’re not fucking a 50 year old ugly dude on steroids.