Good question.Why does making a button look like a button make it better? It's still a flat piece of glass that you're pushing on.
Because you need to know what on the flat piece of glass is touchable/actionable and what is not.
In iOS6, you always knew what was an actionable button and what was not, because the buttons had depth, they sure looked like pressable items and there was no confusion.
In iOS7, you're never sure - there are 2D buttons with solid color fills, 2D buttons with no fill but outlines, 2D buttons with no outlines, titled icons with shapes, and finally text in a different color. And, since app developers can make text any color they like, how can we be sure that the colored/highlighted word is a button or not? Why are some things shown as 2D buttons but others as colored text? Beats me.
Inconsistent as all get out.