It's not worth the support trouble for the little it would make. Adblockers often break legit things too. Often people still want to use links that go through t

It's not worth the support trouble for the little it would make. Adblockers often break legit things too. Often people still want to use links that go through tradedoubler and the like. One support call and your yearly profit is wasted. And how do you block access to non paying customers? DNS isn't autenticated. It's also not really a great method for adblocking anymore (which would make the support problem worse, "why am I still seeing ads?")