Torrents tank when there is lack of popularity. Linux can be configured for a wide variety of purposes, from IoT driver to gaming workstation, so not all packages are equally popular with all people, and just because a package is unpopular doesn't mean it isn't important. If I'm the one person in the world running a service that everyone else relies on, then the packages which support that service are important even if no one else uses them.

Therefore to use torrents requires one of two choices, neither of which are really viable when you think about it. Either:

* Require everyone who uses the distribution to torrent releases of the full set of packages for the distribution. (And remember that packages regularly get updated even in LTS releases, due to backporting security fixes etc.) It means everyone using the distro really needs to be running dozens or hundreds of torrents.

* Everyone torrents only the packages they need, so access to packages becomes up to popular vote instead of actual importance.

Torrents are fine for isos but intractible for ongoing package management.