I just can't imagine many buying a cd just to hear what it sounds like unless they're just getting a copy for the car or ipod.
Some people do not like multi channel music. That whole "The drums are sounding behind my head" thing. Stereo down mixes done by the AVR con be pretty freaky sounding too. Also, most decoding of Blu Ray audio is being done by an AVR, which is often bettered by the users 2 channel set up.