On desktop, pretty much only when I need to access an Onion site.

I also route my Torrent client through Tor, as neither my router nor my VPN allow port forwarding, but I should be able to seed over Tor without much of an issue (still working out the kinks though).

On mobile, I use Tor Browser as my main browser because it provides the best fingerprinting protection, so I'm stuck using the Tor network as a result.