> There is no system to keep content alive so links will still die.
Torrent trackers solved this in a very interesting way. They created an economic system where bandwidth was the currency, incentivizing the permanent seeding of content. It was illegal to take more than you gave. I've even seen an academic paper studying their system!
Bandwidth as a currency eventually proved to be a failure. It enabled the rise of seedboxes, dedicated servers featuring terabytes of storage and connections to high capacity network links. Just like the IPFS centralized gateways you mentioned. They would eventually monopolize all seeding, removing any normal person's ability to gain currency. In some trackers, if you wanted to consume content, your only options were renting one of these seedboxes or uploading new content to the tracker. You always stood to gain at least as much bandwidth as the size of the content you uploaded. The seedboxes would monitor recent uploads and instantly download your new content from you so that they could undercut you. I suppose it was a form of market speculation.
They also failed to realize that there is no uploading without downloading. By penalizing leechers economically, they disincentivized downloading. This led to users being choosier: instead of downloading what they like, they'd download more popular stuff that's likely to provide higher bandwidth returns on their investment. Obscure content seeders would not see much business, so to speak, due to the low demand for the data. Users would stock up on popular and freeleech content so they could get any spare change they could. The more users did this, the less each individual user would get. Then seedboxes came and left them with nearly nothing.
This was eventually solved by incentivizing what was truly important: redundancy. Trackers created "bonus points" awarded to seeders of content every hour they spent seeding, regardless of how much data they actually uploaded to other users. These points can be traded for bandwidth. This incentivized users to keep data available at all times, increasing the number of redundant copies in the swarm. People will seed even the most obscure content for years and years. In some trackers, these rewards were inversely proportional to the amount of seeders: you made more when there were fewer seeders. This encouraged people to actively find these poorly seeded torrents and provide redundancy for them.
We can learn from this. People should be compensated somehow for providing data redundancy: keeping data stored on their disks, and allowing the software to copy it over the network to anyone who needs it. The data could even be encrypted, there's no reason people even need to know what it is. Perhaps a cryptocurrency could find decent application here. Isn't there a filecoin? Not sure how it works.