Understand that the ad industry isn't a monolith. The advertisers shoveling shit ads onto local news websites aren't making some grand bargain for short term revenue at the expense of long term consequences (blocking, etc.). Those advertisers simply wouldn't exist otherwise. They're filling a small niche while they can. The fact that their behavior might cause the whole industry problems over the long term does not matter to them.

Google, FB, et al would love it if these shitware ads disappeared because fewer people would feel the need to block ads. But there's really nothing they can do about it without being shouted down (or worse) as being anticompetitive, regardless of whether that's true or not in this case (and there probably is some truth to it).