Facebook used to deploy their code using bittorent. I doubt it has changed.

A lot of blizzard video games update using bittorent as well. If you play Starcraft 2, you use bittorent.

Streaming services like stremio are basically bittorent. After netflix, it's my main source of video content.

If you want to download the internet archive, that's the saner option. Same if you are a pentester, as a lot of heavy leak or hash db are so huge only bittorent makes it practical. Too expensive to host for one small actor. It's also more resistant to take down notice.

We talked a lot about RSS lately, and how to revive it, while in comments people said it actually never died. Bittorrent is a lot like that. Great tech, great standard, it works flawlessly and fill its use case perfectly.

The only reason it's not more adopted is because it's not in the browser by default. Otherwise the hosting benefit and the dl speed is such that it would be an instant hit.