I would wager that 90% or more of their revenue comes from the generic TikTok meme slurry of r/all and the front page. I think some big % of their users aren't even signed in.

So the long tail of hobby subs are probably just noise and operational burden. So if they're wanting to IPO, they probably want to cut costs and focus hard on ad revenue. I'm guessing banning nsfw stuff is probably in the works too.