I don't understand how more countries don't hold the publisher responsible, especially after they are notified. I'm sure that in a classic newspaper, the publisher would be held responsible for obvious scam ads. But by intentionally automating and outsourcing everything, suddenly that responsibility goes away?

Hold the publisher responsible, let them deal with the ad platform. Suddenly, it becomes very attractive to have an ad platform that doesn't allow scams.

If the publisher and the ad platform are the same, even better.