The volume buttons are designed to work across the entire OS to continually change either the ringer volume or the volume of the song playing in the background. Is it really impossible for you to see how changing the functionality of the volume buttons--that previously have worked like every other volume button on the planet--on a per app basis could be a bad idea? The comparison to the keyboard is laughable.
Only on Slashdot does this tripe get modded up, for reasons that are lost on me. It's like in the fight against Apple, any dissenting opinion becomes Insightful, even if it's idiotic. If there's one thing I'm glad for, it's that people like you who think this is a good idea will all own non-Apple devices. Go ruin the user experience of someone else's device, and keep away from mine.