Yeah not sure what's holding them up a thermostat in the UK is much simpler as normally it's just heating you turn on or off.
I imagine they need time to build up the necessary experience to support the product well. Nest's support, the one time I had to call them, was outrageously good. Within about 10 minutes the engineer had figured out exactly what was wrong with my wiring setup, and, more or less blind, walked me through the discovery and installation of a common wire.