@ Mitsurugi
> How does it make sense in this day in age (20 yrs later) to still have to use my mp3 player and headphones to listen to the music I wanna hear while playing games
But then you can't hear the sound effects. Doesn't outputting through the same speakers make more sense?
> I really hope Sony makes it mandatory for devs to include it in every game
Sony has given developers an amazing amount of freedom (much much more so than Microsoft does), I doubt they will change this. They have given developers the option to include custom playlists, but they themselves have to decide if it makes sense for their game.
For games such as Killzone and Uncharted with dynamic music I doubt they will make use of this approach in the future.
Maybe you can find an interview asking for their perspectives, here's one with regard to the audio in Killzone 2 (but I can't listen to it right now):
http://www.gametrailers.com/video/art-killzone-2/43392
