Steven Aquino writes about the inclusion of button shapes in iOS 7.1 beta 2.

From a AX perspective, what the new Button Shapes do is restore a sense of explicitness to iOS 7′s interface. These types of visual cues are so important to many visually impaired users, myself included. Whereas previously I struggled in identifying whether a label was an actionable control or simply a label, iOS 7.1′s Button Shapes hearken back to the iOS 6-style, This is a button. Tap me!, level of usability. And therein is the point: usability. As I stated, it’s perfectly valid to wince at and decry the visual design of the new buttons, but make no mistake, the addition of this feature is a tremendous improvement for visually handicapped users such as myself. These buttons will make iOS 7 infinitely more usable than it is today, and Apple absolutely should be applauded for addressing a serious issue — not only for me, but even for the normal-sighted as well.

Very good point. It seems that many people missed the fact that the option is available under Accessibility. The inclusion of the ability to turn on button shapes is for the benefit of visually impaired users. The emphasis is on making iOS 7 more usable for this particular group of people, and not on making it look visually stunning for everyone.