So why not just make the video available on torrent?

It's even possible to streamline the experience for torrents like how Popcorntime has done. Users don't need to even be technical enough to understand what torrents are - the same way users don't need to understand tcp/ip to visit a website.

Bittorrent protocol is not supported in browsers. Peertube uses Webtorrent, which is a WebRTC port of the Bittorrent protocol. Those two networks are incompatible but the magnet hashes are the same and there is progress in desktop clients implementing Webtorrent peering.

You can try to think of Peertube as Popcorn Time with user following and channels and comments... and interop with the rest of the Fediverse.