There is a reason why these Youtube channels don't just roll their own platform: their content is not worth money. Same reason why no one pays for your blog. It is just not worth any amount of money.
There are many Youtubers whose content I like, but if I had to pay monthly fee (or pay per view) for their videos I wouldn't watch them. I think this was pretty much confirmed with the Youtube Red experiment. Many of the channels I follow got picked up for the program, but I have no desire to pay for the shows they produced for Youtube.
And how the ads work on Youtube makes it completely unwatchable without AdBlocking and I am not paying for the Youtube Premium to remove ads because A) it won't remove the ads and sponsorships that are embedded in the videos and B) I don't want to give Youtube as a platform any cut.