why would anyone seed on a public bittorrent tracker? It makes absolutely no economic sense - you put yourself at legal risk for absolutely no benefit to yourself, reputational or otherwise. And yet people do! a shitload of them! they'll go very far out of their way to subscribe to VPSes, rent seedboxes, build their own servers, etc. to do it!
Something like chia instead actively punishes freely sharing resources. You have to prove that you are wasting a ton of resources in order to sell some of it. I am not sure if you can "just seed" on chia or filecoin, but why would you when you can waste a ton and sell it? This is true whether the storage is on or off chain.
Filecoin boasts that it stores 4.1EiB of data (on 50EiB of storage) but there are only like 2000 active nodes. Arweave currently has 699 active addresses (and storage is like $16/GB). On the pirate bay, the Wicked torrent has more seeders (7203) than there are miners on filecoin -- and that's for a FILE YOU CAN ACTUALLY GET AND USE instead of some abstract storage economy.
People have files, want to get files, and will share some files too. adding a whole economy to that turns off 99% of everyone - it's antisocial in more ways than one. Protocols don't need an "incentive layer" because that layer is just society and people who want to store and share stuff, and if you let them they'll organize their own systems.