Quite a lot actually. More and more people are working from home, AKA they NEED their Mac to make a living and there's no corporate IT to save them from something like this. If they're mac doesn't work, they can't work so you better believe they'll be hightailing their ass to the Apple Store to get it fixed ASAP.
Yes, those of us who are IT savvy, pros, long time mac/computee users, whatever you want to call it, KNOW that you really shouldn't upgrade a "production" system to a .0 OS release, particularly on day one. But to listen to Apple talk about it, "Big Sur is the best thing since sliced bread and you should update on day one!" Just because you're not convinced doesn't mean their aren't tons of less tech savvy people who are. During normal times many of those people would be protected from themselves by their IT departments, but, during a pandemic that's not how it works.
Furthermore, once again, I want to emphasize, THIS ISN'T NORMAL. BUGS are normal for a day one OS release. BRICKING computers such that even advanced end users can't fix it on their own need to be return it to the manufacturer for repair is almost unheard of.
I don't know why you want to pretend like its ok that Apple bricked these macs just because these people had the audacity to, as Apple always suggests, "upgrade to the latest version of macOS" in this case Big Sur.