I've had my iPad 1 since launch and at first I was very protective of it. I keep a case on it but nothing protects the screen. In the past 2 years I've been less protective of it and sometimes even place things on top of the screen if I'm carrying stuff around. I'm just curious why it has literally no scratches at all when every other device I've had (including iPhones) always manages to get at least tiny hairline scratches over time. Do they use an even stronger material for iPad screens?