This is a wild statement to make so matter of factly.

Do cases guarantee your screen won't break if you drop your phone? No. Do they dramatically diminish the likelihood of cracked glass in the most common scenario of phone falling on flat concrete? Absolutely.

It’s no longer worth the risk though. You need your phone for so much stuff having it break is extremely inconvenient. And given the price of phones, and the cost of cases and screen protectors, theres no reason not to do it.

I have gone through several sacrificial layers of glass to save several versions of gorilla glass (etc). I have also lost several screens later because I wasn't quick enough in replacing the sacrificial glass.

Some of us are harder on our things than others...

I use a case mostly to provide grip. The bare metal is too slick.

Most big screen damage happens from things hitting the edge of the phone. Cases prevent this. Also, the edge is the one area not really protected by screen protectors.