The evolution path of the cellular/smart phone didn’t always need a protective cover. That was a result of smaller easily handheld devices and more fragile components, as well as a convenient add-on product. Remember the earlier Nokia-types and their belt clip-ons for this same dropping problem? Plus they were still a bit heavy for slipping into a pocket.

The reason why the comparison doesn’t work is that there is a century or more of experience and research for cars and similar surfaces exposes to the elements, Tesla/Musk just decided to be different despite the glaring evidence it was a bad idea.