I think size is the biggest factor. OS ISOs are pretty big, so having a managed download is helpful. If the 100 GB triple-A games were open source I would certainly expect torrents. But the FOSS things I download directly are pretty small, and the vast majority are done through a package manager or docker compose. So there may be a Goldilocks zone in the middle where it’d be helpful, but in those cases I’d expect a small installer that downloads the bulk of it for you.

So not much benefit for the consumer, but what about the provider? Spreading the traffic would reduce load on the hosting server which is a positive. You’d still have to handle the bulk of the traffic until the seeders outpace the leechers, but on long enough timescales it’d be helpful. Except you can’t really update a torrent, which means each release needs to start fresh. This still works for OS creators because updates tend to be far apart, there is a large user base, and there is still some market for older versions. For regular programs you may only get one of those three, at which point adding torrents may be more hassle than it’s worth.