Assuming that figure is accurate, it's still missing context. 90% are installed that way right now. They do seem to be betting the vendor install channel will continue to be the dominant channel in the future, and that bet will likely play a large role in the success of the product.
> They do seem to be betting the vendor install channel will continue to be the dominant channel in the future
In many places it will be. Want to buy a Nest in the UK? Guess what, you can't install it yourself: Nest will send a contractor along to install it for you. Many countries highly regulate heating system installation, for good reasons. Even if you're in a jurisdiction where this isn't a problem, the majority of thermostats get replaced along with other HVAC work (new boiler, new pipework, etc), which is going to be done by a qualified contractor.
Since building a new home or building is done through contractors and not likely to change given laws and, well, logistics, if you don't have a contractor channel, your product doesn't get installed from the start.
Source? Isn't that only true due to the fact that most people do not change thermostats in homes/apartments/condos they move into, or when they change HVAC systems?
I'm not so sure. For a home DIYer, changing a thermostat is a pretty simple project. I bought a nice programmable unit a few years ago to replace the old mechanical one, and the entire process took maybe 20 minutes. It's along the lines of "attach the red wire to this screw. Attach the black one to this screw. If you have an air conditioner, put the white wire on this screw."
It didn't involve any tools beyond a screwdriver and the instructions were dead simple. I wouldn't hesitate to install another replacement unit myself.
Only allowing purchases this way is probably folly, but can you imagine homebuilders talking buyers through their upgrade options and all of a sudden having this new world of automation to include? Thermostats, security, A/V, .... Lots of money is there to be made.