Filecoin is probably one of the best examples of a decentralized storage rewarded via crypto. There's also several Defi lending platforms that have helped students paying off debt, although I don't know enough about which networks are the best there.
No. If people are seeding a file that you care about on bittorent today, there's really no mechanism to ensure that it will be available tomorrow besides seeding it yourself.
Hmmm, it doesn't exactly sound like you are "absolutely baffled". You acknowledge that there are astoundingly few good use cases for blockchain.