Funny, I just saw a friend's Android phone get bricked by an update about two years ago. It was in a state I probably could have recovered it from if its bootloader were unlocked, but it was beyond reach of Joe User.

I've also bricked or seen bricked routers, external HDDs, and TVs in the last five years.

Many TVs, actually, if you include pre-release units. As far as I can tell, most of them rely entirely on testing to avoid bricking devices. They make zero provision for the inevitable case where something goes wrong. Power failures during updates remain a frequent cause of bricking.

Your "exception" is quite a common case when firmware updates are performed manually. Those failures have, of course, dropped dramatically since devices started being able to self-update, but they're far from the only such failures out there. The "some reason" depends on the product and manufacturer, but it's usually a combination of laziness and penny-pinching. Somebody didn't want to do the work, or somebody else didn't want to pay for it to be done.

I've seen the processes that lead to these situations up-close. There are a lot of engineers out there who don't think about failure modes, and a lot of managers who dismiss the engineers who do as paranoid and/or troublemakers.