This. It's not the glass specifically (you can still buy cheap androids with polycarbonate screens), but the capacitative touchscreen, which is more expensive and requires a much fancier controller to read. But without it, either you have to use a stylus, which despite Samsung's belief hardly anyone wants, or press fairly hard. And you can't do multi-touch at all.
Capacitative touchscreen + "real" web browser (not WAP!) was the key capability of the iPhone. The fact that it subsumed the already successful iPod was a big benefit too.
> which despite Samsung's belief hardly anyone wants
Which is why nobody is buying ipad pros or surface pros and Wacom is bankrupt /s.
Having a pen in addition to capacitive touch is great. Having only a pen was not. Though the resistive screens in the Nokia N900 or the Nintendo DS for example were not bad.
Capacitative touchscreen + "real" web browser (not WAP!) was the key capability of the iPhone. The fact that it subsumed the already successful iPod was a big benefit too.