Are they? Almost everyone I know has a case on their phone; and I didn't have one until I bought the iPhone XS, which is over $1k and has glass on both sides.
I mean, don't get me wrong; I like the capabilities of the new iPhones. But the current design means that what most people actually use not the slick shiny slimness you see in Apple promotional materials, but thick sturdy plastic keeping all that fragile glass safe.
If Johnny Ives really wanted to be able to see people use phones the way he envisioned them, he should have designed it to withstand a 10-foot drop onto concrete. That would be a lot more useful than 30 minutes underwater.
I don't think people put cases on their phone to make them thicker. I think they use cases to increase durability. Making the phone itself thinner means that the phone in a case will also be thinner, so that's perfectly compatible with the claim that people prefer thinner phones.
2) when set on a flat surface, it creates an unstable bridge, meaning downward pressure on the phone is not supported. Think of how a piece of cardboard would react to being pressed down in the middle with only 3 of its corners supported.
3) It creates a point that can be snagged when moving the phone around, either on clothing or surfaces it's set on.
Personal opinion, it's really frustrating to have a phone that doesn't sit flat on a surface, to be unable to easily use it without some kind of case or holding it.
And if you had a thicker phone, do you think it would obviate the need for a case?
Tried to do the same with my 6S, where the glass goes over the edge of the phone. Cracked the screen 3 times, got a thin case. When I decided I wanted to upgrade to an XS rather than repair the screen again, the wife said only if you get a proper case; and I had a hard time disagreeing with her.
I'm positive that Apple could design a phone smaller than the combined size of the XS a good case, which would handle the drops I subject my phone to occasionally just fine. It would be a little thicker and less pretty than the current phone without a case, but much less thick and much less ugly than the current phone with a case.
// Technically no, technically still inset just enough to not touch the service it's on.
Serious drop test, without any wussie case
I am certainly in the latter camp, in fact, I would prefer an even thinner phone, because I am almost always within arm's reach of a charger and rarely even need "a full day" of battery life.