This only applies in areas that already use electric heaters. Anywhere else poor people cannot afford to replace their gas heater with an electric one. And if they rent they have no choice, it’s up to the landlord. In some locales it is common for the renter to pay for the heat bill. So the landlord has little incentive to install a different heating system. In other locales the average cost of heat is factored in to the price of rent and the incentives are basically the same.

> I doubt a mass produced thermostat that could get a price from the internet would cost more than $10

Total costs will be low if you can also find a perfectly spherical plumber (& electrician (& WiFi/4G-technician)) that charges less than $1 per hour for installation.

>that could get a price from the internet

If we're dealing with rural areas reliable internet isn't always a given. The UK had an interesting solution for this for older electricity meters which encodes data in the BBC Radio 4 LW (198 kHz AM) radio station. Most of the country is covered by a single transmitter because of how efficiently LF waves propagate and it doesn't require an internet connection to work. Sadly I think the rise of smart meters will probably be the death knell for Radio 4 LW too.

I think it's easy to forget how flakey the internet can be outside of major cities in some places. Having lived in places that are fairly off the beaten track I wouldn't want my electricity bill to depend on always having a reliable WiFi connection for example.