I've said it before...
...and I'll say it again.
There is one change that made smartphones ubiquitous and kept their PDA/phone predecessors as niche products. Robust glass screens.
Prior to that, we had plastic displays which would scratch, crack, break or just give up if treated with anything other than utmost care. Always keep it in the case, always use a screen protector (no matter how much this fucks up responsiveness), never put it in a bag with other objects, never let your car's airco play on it on a hot day, etc ad nauseum.
When someone invents folding Gorilla Glass, these things may start to look like a good idea...
Biting the hand that feeds IT
