The problem is that hosting and bandwidth aren’t free and abuse is a big problem. Managing a distributed petabyte-scale archive which gets updated so frequently is a significant engineering problem even for a single party — now consider how you’d handle redundancy and routing when you can’t rely on any of the parties involved, and you have enough different objects being accessed to turn away most participants unless you can guarantee that participating won’t blow your ISPs data caps, interfere with other use, etc.

Abuse is the other huge problem: think about what happens when you’re hosting some BLOBs and the FBI shows up at your door because someone uploaded some kind of contraband and some of it was available from your IP address. How many people are going to setup completely independent hosting accounts to avoid fallout from something like that which happens so regularly?

The closest thing which comes to mind is the Debian mirror network and that is something of a historical fluke, predating centralized hosting being possible, and scoped to a much smaller set of more trusted participants. That also hits the big problem that even with a fair amount of infrastructure backing it, it’s hard to match the user experience of something like Github or NPM so the most likely case is spending a lot of time in hard problems but not overcoming the basic economics, as seems to be happening to IPFS.