To be fair, for some youtubers, their primary source of incomes are Patreon and In-Video Sponsorships, which can be done on Peertube. After all, we've seen some youtubers, notably The Linux Experiment, use Peertube.
The biggest hurdles here would be user base. It'd be difficult to grow peertube's userbase because most creators there rely on youtube as an income-- unlike reddit or twitter where it's mostly unpaid social media stuff, so most would be scared to move to a new platform as it'd be too detrimental to rebuild their userbase.
That and the instance's funding, which, you know...
Yeah, I post more. Gotta do my part to make this community alive.