A Speculative Fiction subtrope of Author Appeal, which is the deliberate creation of a future (or alternate history, or fantasy..) society in which the author's particular kink is "normal". That which is Fetish Fuel to us, is a commonplace to those in-universe. Used a lot in written erotica. Also some porn movies but not as much as you'd think, given that typically porn movies are Porn Without Plot and thus don't even bother with a story to the sex. Sometimes characters of a Fetish Fuel Future will consider the "normal" sexual practices of visitors to be taboo. See also Free-Love Future.