Personalities of models. Lol, that is some niche market my dude. Never watched a porn a said to myself "wow, I really like her personality". It's just smut to beat my meat to, nothing more, nothing less.
That's the thing though paid porn is niche to begin with, and for people that pay for it there are three groups. Group 1 that cares about production quality, group 2 that has some hyper-niche fetish, and group 3 that wants more than just something to best their meat to, they are looking for a sexual parasocial relationship.
Your future of ai porn of anything and everyone could only address group 2. Group 1 will take quite some time before they are satisfied with generated porn (it would need to be indistinguishable from real 4k porn with high production values.) and group 3 would require the computational power to render it in real time with both a believable personality and high quality graphics.
Probably because the subtitles have their own copyright separate from the film itself and Amazon likely doesn't have the license to the English subtitles outside of the USA. It wouldn't surprise me, music lyrics have their own separate copyright from the recording after all.
The copyright system is the biggest problem here. It simply isn't fit for purpose in the digital age, unless that purpose was to benefit a handful of legacy mega corps while harming independent content creators and stifling culture across the globe.