Normally I'd agree, but the current crop of devices demonstrably have exactly that problem - they get disabled because of chronic false-positives. So some improvement/complexity is called for.
It seems to me that as usage increases, the Nest team can use that data to come up with additional features that could incrementally increase the safety of your home over time, however small that increase might be. The obvious caveat being that the updates need to be safe as well, but I think the long tail of a product like this could be increased safety over time, which to me sounds attractive.
Not to mention the benefits this adds if you already use a Nest. We have two in our home and the ability for it to know more about the temperature in different rooms is something I've wanted since we installed them.
[1] http://support.nest.com/article/Do-I-need-Wi-Fi-to-install-a...