Why not implement it to other devices too?
I can only see the price of them being a problem, I guess...
But I'm sure the general audience would see attraction in such high speed transfer of data on their devices, crossing music, films, etc. to their device in a matter of seconds.
You're assuming that they use high speed/high performance flash in the iPhone - they don't which is why you'll never see a USB2 connection flooded when syncing with an iPhone.