Because it is a federated video platform completely independent from YouTube and Google. So Google has no say on what goes on it, who gets to post, how it is administered, etc.
I mean if you watch The Linux Experiment then yeah, and only because he chooses to upload to both YouTube and PeerTube (different instance). Generally speaking though, most of my favorite creators don't upload there. Yet...
isn't this a whole different site?
Correct, and that's why it's so important to get creators to put their stuff on PeerTube!
IMO, PeerTube is the long-term solution to YouTube. Eventually, they will block Invidious, break FreeTube and NewPipe, and generally make YouTube unusable for people who cannot afford to pay and/or give up all privacy to Google. Or, knowing Google, they might just kill it for funzies.
We need to learn how to use PeerTube, and we should convince creators to upload to PeerTube in addition to YouTube.