Sapphire crystals are still used for the lens covers, which makes sense, because if there's any component of your phone you want to provide with extreme protection, it's the camera lens.
A screen can work fine with a crack or a dozen, but a cracked camera lens? Game over.
I wonder why there are still no widely available sapphire crystal screens.
growing a sapphire crystal is difficult, and like silicon chips, the bigger the surface area, the chances of defects goes up exponentially. Additionaly, ading $200-300 to the BOM to make your product last longer is a bad idea, since each broken screen is usually a sale or a $500 repair bill. simple economics.
I wonder why there are still no widely available sapphire crystal screens.
Two reasons: large, phone sized sheets of sapphire are difficult to manufacture and be optically clear. Also, sapphire is more brittle than glass... so despite scratching less easily, it's much much more likely to shatter if you drop a phone. Glass, as much as it has deficiency, is a compromise inbetween. And it's way cheaper, to boot.