Something big is happening, as Reddit seems to have purged literally every NSFW sub they know. Reason is always "unmoderated" despite some of the banned subreddits being fully moderated.
Edit: seems to have been a bug in automation (thanks @lefty7283@lemmy.world):
https://old.reddit.com/r/ModSupport/comments/1ii67mt/_/mb3fewv
It's still a good reminder on how quickly a community (or communities) thousands of people enjoy and in some cases rely upon can disappear.
As I have seen it pointed out, it's not just that, although it is a huge part of it. Another, sadly, is that there was so much uncontrolled porn floating around the internet, much of it was pretty fucked up - involuntarily filmed and/or published without consent, not traceable, even with very unclear ages, etc., etc.
So as a secondary effect, that I think is highly positive, most sites also just don't allow for non-verified content, or at least are much better at removing anything remotely suspicious. That leaves the OF stuff as the main non-studio-produced source, as it allows for easy, professional verifications.
You don't have to be verified to to post nudes on Reddit