Most of them have Patreon for that, which actually produces income.

What's the incentive? All they would be doing is pushing views away from platforms where having viewers actually benefits them, either through metrics or income or both.

Honestly the best way to get that going might be to have a company and offer sponsorship deals with the requirement that creators also post to Peertube. But that would require companies having a reason to want people on Peertube.