>Everything ever written to the Bitcoin blockchain is still available
This isn't useful for 99% of stuff and pushing every video and music file on earth through a global state machine with the performance characteristics of an Atari from the 80s would render the thing inoperable. The entire Bitcoin network has a bandwidth of like 1mb every 10 minutes, the total size of the blockchain is half a TB in total, people torrent more porn in the time it took me to type this.
Maintaining a global, complete history of transactions only ever made sense for one problem, double spending, and is utterly useless for sharing files.
IPFS is not a blockchain in the traditional sense. You might be conflating it with Filecoin.
What do you mean with "torrents work fine"? Do you have any statistics on the lifetime of torrents?
Everything ever written to the Bitcoin blockchain is still available and massively distributed. It seems very unlikely anything will ever get lost during our lifetime. So I would say that is an example that monetary incentives do work?