Best way I have heard it explained: The A7 is the chip of tomorrow; not today.
All of the side-by-side comparison tests show no significant real world performance benefit to the A6 in the iPhone 5 (basic OS use, no gaming). By the time the 64-bit architecture catches on and is fully realized by developers, the iPhone 6 will be looming around the corner...
Yes they do. The A7 is noticeably faster in many apps, not just gaming. iOS 7 stutters a bit on the iPhone 5, no stutter on the 5S (in multitasking) - but this is probably due to lack of optimization.