Yet none of them know the difference between hardness and brittleness. Even a noob (real) machinist knows more metallurgy than that.

We have to face facts. Modern american cell phones are basically the same economic era as pre-imports american cars. Much as domestic cars were value engineered to rust out in two years, at least until the Japanese conquered the market, we're going to have to tolerate expensive phones that are designed to fall apart until the (Chinese?) import phones that survive twenty years and everyone else has to catch up to them. A glass back is to cell phones as tail fins are to cars.