As far as I know, it was manual, but that was already a few years ago.
I don't remember the name of the company, but surely it can be found and there are probably multiple such providers. The service was provided to TV operators (satellite, cable or pay-TV) to include in their set-top boxes.
PS: of course, as sjcsjc mentioned in a sibling comment, it immediately gives the idea to many people to only show those parts :)
https://en.m.wikipedia.org/wiki/CleanFlicks
There's a documentary about it: https://m.imdb.com/title/tt1007026/
My 14 yo would be very happy to select those versions.
It makes me smile to think that my 15-year-old self would have loved a feature that did the same but in reverse. That was, of course, a pre-internet, almost porn-free world.
How about when the extra scenes are literally useless to the point of the content and are just "wedged in" as fanservice to increase viewership, in a way where the content is better off without them? This describes nearly every sex scene in a Hollywood movie that I can remember.
Though also, separately: I'm an adult, but I'm imagining going home for the holidays to my parents, sitting around at night, picking some movie to watch on Netflix, and it ends up having a sex scene in it. I don't want that to happen! It's not a matter of maturity—I just don't want to share the experience of watching a sex scene with my parents. I'd rather be able to tell Netflix/the streaming box/the TV, to skip those scenes.
No- nudity