1 Muting music doesn't make the client play a different song for you. What OP is asking for is the client to display different clothing.
2 Bard music can interfere with the game's actual music by clashing with it and sometimes making it difficult to even hear. A player's glam can't interfere with how another character or npc looks unless they literally stand on top of them. The mere act of having a glam on its own doesn't change how another player or npc looks.
3 If you're listening to audio that is playing from a different source (youtube/itunes/etc) the game's music and sound effects can interfere with how that sounds, or even your ability to hear it. A player's glam, for obvious reasons, cannot interfere with how something else displays in another piece of software.
So yea comparing being able to mute sounds with removing other players glams is a false equivalence.