> No one I've talked to is actually interested in the step-sibling fetish, yet the overwhelming majority of content being made and advertised - especially by mainstream studios and well-known actors - is step-sibling themed. Why? Because these studios are deciding what to make based on what's popular on pornhub, and what's popular on pornhub is literally anything these studios make. I sincerely doubt that they would see a drop in engagement if they diversified, but trends in data will never drive diversity faster than they drive convergence, because convergence is essentially the goal of data driven production in the first place.

I think your analysis is incorrect... it's likely extremely profitable for the porn studios because: 1. It's an easy plot to make up. 2. requires absolutely no extra props fancy locations or anything beyond the basic porn shoot. 3. it's extremely taboo so for whoever is actually into that they get to rope in and for the rest of the porn consumers they can just skip the part where they have all that verbalized and it's basically normal porn for some version of normal.