I don't imagine this was a 100% their decision, it's more like a response to the epidemic of all the world's governments suddenly coming up with adult verification schemes. Discord has already required it in some countries, and it's definitely easier to get everybody to verify themselves than require it on a per-jurisdiction basis. The personal data they get is a cherry on top.

Also, this is just the beginning, more social networks will require the same soon.

They don't have to comply in advance.