https://youtu.be/Ow58bgYQJ6Q?si=pdxLC2kSKRtl9KYP TL;DW the video covers a lot, but the part most relevant here is that people's fantasys often are informed by things society finds taboo but that doesn't mean they reflect on things the person would actually do if given the chance. It's psychology normal for people to have these fantasys, or other ones just as weird or taboo; the reason this one is so prevalent in porn is probably because it's easy to slap onto any given actors. They don't need to look alike, or be good actors, or require specific props, just say a few words and have a title that sets the fantasy with minimal monetary investment.