"If your smart thermostat goes wrong, you could end up roasting or freezing. If your smart lock goes wrong, anyone could enter your home. If your smart lighting goes wrong, you could up in the dark, or with rooms suddenly lighting up. And if your smart smoke detector goes wrong, you could end up in a panic in the early hours of the morning."
Things that pretend to be smart but are incapable of detecting themselves going wrong for the most common failure modes*, just aren't.
* I can accept them being unable to cope with weird edge cases, but low batteries?