In my (recent) experience, Honeywell owns the HVAC contractor market, which is where these decisions are being made on installation, repair, and maintenance.

Limited sample size but between three furnace + air quotes proposed in August 2015, all three contractors recommended the Honeywell and all three contractors dismissed the Nest as a gimmick with lackluster functionality compared to the Honeywell.

Over a year ago, Nest was selling 100K thermostats a month:

http://www.businessinsider.com/nest-revenue-2014-1

I worked at Nest on their professional distribution channel for some time. The thermostat market is dominated by professional sales (80-90% are sold and installed by professional HVAC contractors) whereas Nest traditionally sold through to a consumer/DIY audience. Nest has a very steep uphill battle against Honeywell the way Apple has had an uphill battle against Windows in large enterprise. Nest just has more mindshare amongst the tech/early adopter community.

I don't disagree its an uphill battle. I'm arguing that Google is a cash machine, and Honeywell is not. Google could continue forever trying to push Nest if they wanted to.