They do it if they think you're underage and it's optional. If you don't do it, you can't see nsfw. That's pretty much it. They also switched away from the sketchy id checker. I'm not saying it's good, but you can avoid it.

Hmm, I'm at the server limit (in 50 Discords) and none of them were marked in that way. Some of them have NSFW channels that I can't access anymore, but I don't care about that.

Maybe I'm in different kinds of communities.

I heard a cousin of a friend saying if you connect via a Moldavia VPS there is no age verification for Reddit (there is, however, for Discord).

Ideally you won't, the requirement sucks