There's also many users who don't need a case. A lot of ipads are POS systems that are fixed to the bench so they don't need a case either.
Given that the impact-absorbing parts could be [0]
...rubber on the edges where impact protection is needed.
and could obviously be designed to be replaceable, either by a handy user or an Apple Technician, why wouldn't you want Apple to design the feel and balance of a device with a case that has built-in impact protection?Apple's decision to make most of its handhelds out of various grades of "fragililum" has boggled my mind since they sold the first iPhone with an easily-shattered glass back. That choice makes sense for a conspicuous status symbol that people are going to take very good care of... but most folks either end up with one with damage that makes plain how theirs is not the kind of life that makes that possible, or they have installed some aftermarket shell that ruins the effect by covering up the conspicuously fragile part of the hardware.
My mum's Samsung S23 Ultra has a ridiculous camera bump and rocks back and forth when you use it, even with some thinner cases. You need a super thick case for it to stay stable.