I've never understood why people want to blare music over their game- when I play I actually use the audio cues to help locate characters trying to flank or come up from the rear and that's not possible when you're masking those sounds with external audio.
I'd also rather not have the game servers have to commit bandwidth to streaming music in addition to the game content when it much easier for the minority of players who want to charge around running and gunning to music while getting ambushed to simply use personal devices and music sources.