Etree (https://www.etree.org/ ) is the longest running torrent site for tapes. It looks like only about 5% of the hundred thousand torrents have any seeders at all. Not sure how reliable requesting a seed is. I’d expect long tail stuff to get “effectively lost”. Versus IA whose purpose and funding is preservation, in addition to sharing.
Thus they are encouraging amateur third parties to pick up some of the archival slack, that style of torrent could outlive IA in case anything happened to them, and it reduces some of their bandwidth costs