Originally Posted by Rach
...if I'm wrong, why was there a need for DVD-A, SACD and now Blu-Ray DTS-MA music discs.
Certainly not for the reason you apparently believe. DD & DTS can do multi-channel but are heavily compressed. CDs are uncompressed but only do 2 channels.
DVD-A, SACD and Blu-ray music discs can do both: multi-channel AND uncompressed audio. That's why there was a need for those delivery media, to overcome channel limitations of CD and lossy compression of DD & DTS.
I don't know where you got the idea that CD is "more compressed" than DD or DTS, but it's not true. RobertR and thehun are correct.