How do you propose making a device that people wouldn't feel the need to put a case on? You could make the whole thing out of rubber but that's still going to take cosmetic damage that people want to protect the device from. You could make it easy to replace that rubber... but at what point is that not just functionally the same as a case?

One way would be to have an accelerometer detect that the phone is falling, and have tiny spring-actuated bumpers, wires, or feet extend from the corners of the phone to catch its fall. Little stainless-steel or Nitinol wires would do great.

Here's a patent for the idea which just expired this year: https://patents.google.com/patent/US7059182B1/

Apple also patented some versions of this, although I think not as nice as the 2005 one: https://patents.google.com/patent/US9571150B2

I bought a cheap(£150 at the time) phone 3-4 years ago called "Ulefone" where in a sense the 'case' is built in to the phone. It is marketed as a phone for handymen or outdoor functions.

It is a bit bigger with protective shell around it is bulky, but withstood all the drops that a typical phone would break. There is some flaring around the screen and camera that it prevents most of scratches. The back has some sort of hard rubber but it held up well.

I've only had to replace the screen protector within 3 years as the scuffs and marks made it difficult to see in well-lit environment.

> How do you propose making a device that people wouldn't feel the need to put a case on?

If the screen were reasonably scratch + shatter proof, I think most people wouldn't feel the need to wear a case.