Probably because it's all an integrated module, and iDrive uses the audio system's amplifiers and speakers for BMW Assist, BT and its bongs and gongs. I imagine the non-iDrive audio system is never actually "off" either when you hit the "power" button, even though the display turns off.
Originally Posted by Snareman
Yea, I've never understood that. For all intents and purposes its off, but really its technically just muted. Odd...
2014 335i Sedan 6MT
Estoril Blue | Black leather | Dark Burl Walnut
M Sport | Premium | Driver Assistance Plus | Technology | Dynamic Handling | Cold Weather | 19" 403M Wheels | M Sport Brakes | Harman Kardon | Rear Window Shades | Auto High Beams
09.16.13 European Delivery
2011 335i Coupe 6MT (ED)
2010 135i Vert 6MT (ED)
2007 335i Coupe 6MT (ED)
2006 325i Sedan 6MT