It's 2026 with 18 different kinds of communication between devices and it's still annoying to get a file from one computer to another *without a central server*.
This is the network effect problem hiding inside a UX problem. The file doesn't care what route it takes — the constraint is trust at the receiving end. The 'no central server' design means you're solving for authenticity at every hop instead of outsourcing it to one point. That's why ad-hoc P2P keeps getting reinvented: the topology is correct, the primitives are just still immature.