"Nest is being run independently from the rest of Google, with a separate management team, brand and culture. … For example, Nest has a paid-for business model, while Google has generally had an ads-supported business model. We have nothing against ads — after all Nest does lots of advertising. We just don't think ads are right for the Nest user experience."
This falls in line with Phil's follow-up on the issue. We may very well see ad-supported appliances in the future, but that's a broad and general assumption that can't readily be applied to the near future with Nest.
That said, down the line would you pick up a connected thermostat that was $50 cheaper than Nest but subsidized by ads? Is there any amount of savings that would make it worth having a blender suggest a nearby smoothie place to you?