Again, the sound quality is not the same as CD; I don't know why you're ignoring this because it's a show-stopper. Because of this, you have to buy 2 copies of everything: MD and CD. Otherwise, what's the point of having a nice home stereo system if you're going to play shitty-sounding music on it? Sure, in the car or in public you might not notice the difference, but at home on a nice system you will.
We already had a lo-fi format available: cassette. Why bother paying a lot of money to go to another format that also has lousy sound quality when you can just buy a CD?