I think like surround sound. Front speakers play slightly different sound than back speakers, same with left and right, top and bottom, subwoofers, etc
This would obviously be fixed though, not head tracked like with AirPods
But you do pay your phone company a monthly fee for the data service.
You can use Apple Music just fine on a Tesla through your phone too, of course, just not via CarPlay (although CarPlay support for Tesla is rumoured to be coming soon)