iOS is no longer in the position of having to teach anyone about touchscreens. Even three-year-olds get them. The smartphone’s greatest problem today isn’t teaching people that there’s a virtual space for doing everyday tasks. Rather, it’s teaching people that they no longer have to use their computers anymore. The functions of phones themselves are growing even as the actual size of a phone screen is approaching its natural limit. Smart phones have, in many ways, exceeded the metaphors that used to define them. Thus, in order to do more complex interactions on the screens, and to keep those interactions uncluttered, you have to strip down the design language.
Cliff Kuant's piece for Wired chimes with what I wrote last night. In the new, modernist, design language, pixels are pixels and the UI metaphor has a different job to do. The headline is rather sensationalist (it is Wired after all!), but once you get past that, it's definitely worth a read.