That's quite a first sentence. I always felt that cases are expected and the design is based on letting the user decide what the case will be like.
I also would like to add that in all my years of smartphone usage (probably about 4 years, quite late adopter) I never broke my phone or screen.
A simple plastic screen protector might be, but those always get bubbles.
Sure there is a thriving aftermarket for phone cases that emerged in late 00s, but it is certainly not an expectation on the manufacturer side.
Thinking about, idea doesn't sound too bad.