The amount of computing power you would get from the machines connecting to the network is so small, that it wouldn't be worth it. No one mines Bitcoin using normal PCs anymore because their hashrate is miniscule compared to a single ASIC.

Paying via lightning is the only option that makes sense. However, many (if not most) phone plans already offer unlimited data. Many places, like Starbucks, offer free wifi. I don't see anyone wanting to pay sats for wifi if they can just use their phone or go to a nearby Starbucks or library with free wifi.