It’s data cost. Private torrent sites are the exception, but most people who torrent don’t continue to seed for a long time, which means that availability is low and the bandwidth cost is usually split among just a handful of users with a seedbox, which is basically getting back to the idea of a server. How do you motivate people to use up their bandwidth and pay for the extra electricity to keep the availability and speed reasonable?
The most similar thing I can think of to what you’re talking about is i2p, but that comes with all the speed and connnectivity problems that are commonplace for the dark web, and the vast majority of mainstream users have no interest in engaging with a complicated P2P network that serves content at speeds that make you feel like you’re living in 2003.
Unless the mindset of the general computer user changes, we are unlikely to see any system take off that doesn’t rely on a central team of motivated people to do the backend work that the users simply don’t want to worry about.
I like interloper.