It really depends how their careers go. The AV studio they sign up with decides how well they think they will sell and basically says "you need to do X if you want to be on our label". For some girls that will be just sex because they are conventionally attractive, for others who are more niche it might mean going direct to no-name nakadashi videos.
Then as their career progresses the studio will look at sales and say "you need to step up by doing X" if things are not going so well. Also some girls decide for themselves. Maybe they want to get a last bit of cash from a good seller (first nakadashi videos do well) before retiring or maybe they need some extra money for something.
When they move from the major studios to uncensored they sometimes change as well. I have a theory, it's because of the non-AV work they do. Like maybe they join a soapland or hostess bar where the other girls do nakadash and decide that it's okay, especially with the guys who have been properly tested. It's also the last chance they have for an AV career in many cases, few come back from doing uncensored unless their censored videos suddenly pick up sales for some reason.
