YouTube as a service has very different performance expectations than something like bittorrent. for one thing the directory function is built in and not externalized to another set of directory services, which are notoriously unreliable in the case of BitTorrent anyway.
And unlike BitTorrent or Mastodon I don't only want to know where I can find a given file, I want to know where I can find it delivered immediately, consistently, smoothly, without hesitation, in a variety of cross encoded formats I'm almost certain to have supported on my device, and with some sort of consensus mechanism to establish a better than chance confidence that the file I start streaming is the file I expected to stream and not something else with the same filename.