It is the same as high speed data (faster than DSL) needs a better quality cable than standard telephone cable. I live in a rural area and have never gotten a faster connection than 43.8kps on my 56k modem. I usually average around 38.6K. The quality of the phone lines is just too old here. I can get digital cable TV here. However, they had to install better quality cable in the ground to get it to work. The old cable TV lines could not handle the digital TV signal well enough to actually see the improvement.
I am actually on your side in part. While I believe a good digital cable matters, I doubt is it as crucial as an analog audio signal.