Your comment actually made a light bulb go off. It makes total sense that Apple would be highlighting their major piece of software rather than the hardware elements...after all we all know what's just around the corner - but also what's still on the shelves.
This is because they cannot compete on the hardware elements. There is no piece of tech on the iPhone 4S that competing smartphones do not do bigger and better.
Screen size
Screen resolution
Screen color gamut
Battery life (hello HTC One X)
Cell phone radio
Storage space
Build quality
Processor speed
Memory
etc.
Apple has at least one manufacturer gunning for them in their ads (Samsung poking fun at the iPhone lines and comparing iUsers to sheep), so they have to exercise a little bit more tact with how they promote their product.
If they talk about how sharp their 'retina' display is then you'd better believe that Verizon/AT&T reps will tell them why/how much better the 720p Super AMOLEDs are when they are in the store.