It also frustrates me that phones are slippery by default and have buttons on the sides which parents inevitably push by accident when receiving a phone to look at photos.
Phones are thin! The case makes them reasonably sized. Treat a naked phone the same as you would a naked human: unsuitable and unprepared to go outside.
In some ways, the best design is still my old Motorola Milestone. Rubberized steel, and indestructible. No case needed. Small, better looking than anything in a case, and it had a sliding keyboard to boot. I still miss that.