Though it makes sense for phones to have a cheap shell that you can swap instead of the $1000 device itself taking damage. The alternative is to build insulation and bumpers into the case that you can't swap. I don't think that's better.
I tried to go caseless back when I was 22 and thought anyone would care how pretty my phone was, but it was slippery and accumulated damage for no reason. My next phone, I kept a case on it and when I sold it after a few years, it looked good as new.
I suppose something that's going to live in a case has no real need to be so beautiful. But it's also a luxury consumer good, so "we cut some corners, so it's ugly, but it's in a case anyways amiright?" isn't really the best marketing message. Also, clear cases seem quite popular for those who do want to show it off.