Let it be clear from the start that this is nothing but pure speculation. I don’t know anyone at Apple and I have no inside information. The only thing I am guilty of is entertaining this thought I’ve had for a while.
The designers and engineers at Apple are regarded as smart people. Why would they think that going to the extreme end of flat user interface design—as they have done with iOS 7—would be a good idea? What do they know that we don’t?
Being able to render almost every UI component as text or a series of thin lines is a beautiful idea, in theory. In practice, fewer means to define hierarchy also means fewer ways to convey affordance.
Tapping on a piece of text performs an action because the text has a different colour? That’s it? What was wrong with having a button look like a button? A hint: the new system wide text size setting in iOS 7.
The problem with buttons looking like buttons is that so far, most of the time, they have been created using bitmaps. Bitmaps don’t scale to other sizes too well. Text, on the other hand, is nowadays drawn using vector fonts that scales very well. In iOS 7, text can even automatically get slightly different weight based on at which size it is rendered.
Using the system wide text size setting it is possible to make the user interface texts in apps on the iPad mini and the iPad Air be the same physical size, despite the difference in screen size. Are you thinking what I’m thinking? Resolution independent user interface. Rumours of oddly sized iOS devices can no longer be dismissed solely on the notion that the user interface won’t hold up.
And finally, a wish: make the text size setting in iOS affect the size of the CSS em unit in Safari. Please? :)