The thermostat isn’t a device that needs annual maintenance or regular tune-ups. Sure, it may need to be dusted off or have its wiring tightened up, but for the most part, it kind of just does what it’s supposed to without much trouble.
So while it’s rare for thermostats to break down or stop functioning, it’s not uncommon for people to replace their thermostats entirely. Why is that? Mostly so they can get something better.