YouTube permits a lot of demonetized videos they don't dare to sell advertising on, or (previously) that YouTubers wouldn't give permission to sell advertising on, because the alternative of erasing the videos would send the YouTubers and their viewers to DailyMotion or Vimeo. As long as the demonetized viewers occasionally watch a non-demonetized video, or the sometimes-demonetized YouTubers occasionally make non-demonetized videos, YouTube makes more money that way.
That's a weaker incentive, though. And it comes with a risk of occasional scandals that scare away advertisers, at least temporarily.
I don't think incentives are enough to predict what YouTube will do. The future is uncertain, there are a lot of policies that could plausibly make money, and the decision-makers are people who read the news and have opinions about what's right, not paperclip maximizers. Politics matters as well as economics.
