Every time someone downloads a book from a shadow library like Library Genesis, it's through IPFS most of the time, often via an IPFS gateway such as Cloudflare's IPFS gateway, so you don't even notice it's using IPFS. These shadow libraries have millions of users per day, especially academics.
You bring up a valid point though. From my experience, IPFS suffers from a tragedy of the commons issue. It's performance is generally terrible because the free providers are overloaded.
> Every time someone downloads a book from a shadow library like Library Genesis, it's through IPFS most of the time
I would like to see evidence this is actually true. My theory is that IPFS's "success" in hosting Libgen is roughly turning ICO proceeds into free hosting. Paying for dedicated servers might have been more cost efficient and, given the performance issues, more robust!