A button requires you grab a chair or broom to activate... and that can be dangerous. Additionally, those test buttons work for 2 mins before it starts sounding again.
Some smoke alarms have the battery holder in the front - pressing a button opens the battery holder and turns off alarm power. This is a de facto hush feature, albeit less safe than a hush button (because people will often forget to close the battery holder, leaving the alarm disabled).
I do not understand why people buy the cheapest possible smoke alarms for $8 rather than spend $13 to buy one with a hush button or $20 to buy one with hush + lithium battery (~10 year) built-in, e.g.,
http://www.homedepot.com/p/Kidde-10-Year-Lithium-Battery-Ope...
In a very small condo I have two smoke alarms upstairs, two downstairs and an extra one that I just put here and there for fun (for instance, in it's current location it tells me when my neighbor is smoking outside his back door adjacent to my unit). I also have a CO alarm that _never_ goes off unless I'm testing it.
When I was a condominium association president I first offered free smoke alarm batteries. I soon realized that some would not ask for batteries and others would remove them from units. So instead I offered them an upgrade: new smoke alarms with hush + lifetime lithium battery which they could not disable without destroying. Problem almost solved: when in a unit I would sometimes find the new smoke alarm lying on a counter, uninstalled. I then offered to install alarms.
I was, of course, not surprised to read today's drudgereport headline: "FEDERAL GOVERNMENT: American adults dumber than average human". We now seem to live in an idiocracy:
The nest thermostat on the other hand is one the top of my list if/when I get my own long-term home.
[1] http://support.nest.com/article/What-types-of-alarms-can-I-s...