Their build quality is shit. I had a phone that I would throw into the air and let it land on concrete for funsies. That phone lasted me 5 years. It was a Motorola. The back was plastic, the front was either gorilla glass or plastic. Either way, I didn’t have a case on it, and it didn’t break.
If a phone needs a case, its because the build quality is absolute shit. Every phone should be able to be slammed onto the concrete without a case. It’s the gold standard of build quality.
Build quality implies durability. If you needed to put a case on your car to protect it from normal abuse, you’d say the car was poorly made.