TBF, over 15* in Germany I’ve only seen a couple of actual thermostats. The vast, vast majority use a valve on each radiator. There are electronic solutions for the radiators, but sticking a Nest on the wall is going to do nothing for someone unless the customer installs specific hardware that the Nest would have to support
*edit : years
Those “valves” are, in fact, thermostats. They use thermal expansion of wax to open/close the valve to get to their set temperature. Settings 1-5 are 12, 16, 20, 24, 28 Celsius.
Yes, but they are not electronic and they don’t reflect the temperature of the room like a wall thermostat does.
They don’t (usually) display the temperature but they definitely sense it, and react to it. When the sensed temperature is at or higher than the set temperature, the valve will be closed, if it’s lower it will be opened. Mere valves can’t do that.
That’s what a thermostat is: A negative feedback control system regulating sensed temperature towards a setpoint, and keeping it there. They’re simple, inexpensive, reliable. Yes having the temperature sensor right next to the radiator isn’t ideal but unless the room is quite large that’s not an issue. Also with large rooms you probably have more than one heater and thus thermostat. And you could, in principle, put the thermostat far from the heater but I’ve never seen that done.
In the Netherlands, almost all houses have a thermostat. I don’t know anyone that doesn’t have one