[hderms]

Presumably none of these big players want to charge money for a pro service because it would be difficult to walk back on w.r.t ad revenue. The ad purchasers would probably take issue with it, especially given that they're explicitly valuing their user base at presumably less than they're charging for advertising access to them.

Not to say it couldn't work, but I'm guessing the reason it hasn't been tried is at least partially do to there being no going back