I think the reason they don't is because the overlap between users with the general internet savvy to use an ad blocker and users who have the general internet

I think the reason they don't is because the overlap between users with the general internet savvy to use an ad blocker and users who have the general internet savvy to literally never pay attention to or click on ads is pretty high. It's sort of the same problem reddit had -- There's just no way to monetize users like this other than locking the entire service behind a paywall for everyone, shutting out the much more lucrative remainder of your customer base.