Why verification is hard
A blockchain can easily verify that a piece of cryptography is correct, but it has no direct way to see whether a wireless hotspot is actually providing real coverage to real users, or whether a claimed GPU is actually doing useful computation. This is often described as the challenge of proof of physical work: finding a way for a decentralized network to verify that a contributor is providing genuine, useful physical capacity rather than gaming the system to collect rewards.
The difficulty is that physical claims are much easier to fake than digital ones. Someone could report fabricated coverage data, run hardware in a way that technically satisfies the network's checks without providing real value to anyone, or otherwise exploit gaps between what the protocol can measure and what actually matters to end users.