> It's so bad that I have to assume that Cupertino is filled with people who "hold the phone differently" and tap with their long fingernails or the very tip of their fingers or something.

Fingernails won't trigger a touchscreen. They do matter, though - as your fingernails get longer, you're forced to tap the phone with the side of your fingertip (so the nail doesn't block you) instead of the front.