The problem with that is that the premium users then become a more valuable ad target, and the free users less valuable. So you have to charge even more making them even more valuable. Eventually you reach some equilibrium. But by this point the premium users are such an attractive ad target that the platform eventually starts sneaking in an occasional ad, and then more frequently etc…

Cable TV used to be ad free when it started out.

HBO is probably the best counterexample, but if you look at what they’re doing with HBO max, even they might not be able to resist forever.