Of course every carrier wants you using wifi instead of their network. Its not their expense, but you would still be paying them for it. But people are not subscribing to often ludicrous mobile plan bills to be told to not use it.
We absolutely have the technology to provide a huge swathe of people broadband (as per the new FCC relabel) Internet access through long-range transmission based tech like GSM CDMA or WIMAX. That makes it insane to propose laying physical wire in the dirt or making an interconnected mesh of low power wifi routers as a substitute. The only real barrier is the draconian privatization of photons that makes up spectrum regulation. If we had a 95% open spectrum with some restricted for government and emergency communications you could easily have broad spectrum towers that could adapt to congestion and pair them with radios that will adapt frequency to optimize for range vs data rate vs congestion.
The limitations are entirely artificial and that should be pissing people off.