> popped the breaker for the sockets causing everything to be harshly powered off. My fileserver took it badly and one drive died.
Maybe someone with more hardware knowledge could chime in, but my default assumption would be that the hard drive died either because it couldn't take another power-off/on cycle, or because the event that caused the circuit breaker to pop was harsh enough to damage it (not sure how much the computer's power supply insulates components from things like that, but intuitively, there are much more voltage-sensitive components in PCs than hard drives). While a UPS might have been effective against a surge, it would not have saved the drive from dying by power cycling.
My hypothesis is that most equipment doesn't need to be notified when on UPS, it could in fact be harmful when it causes a power cycle that turns out to be unnecessary. An orderly shutdown doesn't matter that much unless you're dealing with an app that can become internally inconsistent, such as a database. In all other scenarios, the journaling FS takes care of data integrity.
So, especially for home use, why not just let the UPS run until it's out?