Robustness??
" even if you're using one of those rugged Otterbox protectors that make your once-svelte phone look like a Panasonic Toughbook on doughnuts."
One thing I don't understand in modern phones.... they are made super svelte, and glass to the edge plus water-repellant coating make them both fragile and incredibly slippery. Which means most people put their phone in a case, making it more bulky (but without being able to use the extra bulk for a larger battery), and denying the benefit of having edge-to-edge screens (or, even worse, covering part of the screen). Moreover, making it thinner makes it more expensive since it's more tightly packed = trickier to design and assemble. Plus, you have to pay even more for the case / screen protector.
The only benefit of this arrangement seems to be the swappability of cases - so are we back to the early-millennium Nokias where case-swapping was a design feature?