Many Many reasons!!First, cable materials. Silver wire BLOWS away copper. Second Silver wire really does blow away copper and third, copper wire is inferior to silver wire because of....
The chosen dielectric (between the signal wires and the return/earth) is PE for this has nearly the same dielectric constant (ε) as PTFE (2.26 against 2.1 [compare: vacuum = 1, PS = 2.6, PVC = 2.9, ABS = 2.8-3.8]) but it is far more easier to process during manufacturing and more flexible.
This mechanical construction leads to a very natural sonically behavior of the cable and a very low capacitance.
Distortion of the audio signal due to interconnect cables between audio equipment is in essence the most relevant factor when looking at the different cable brands.
The use of a rather complex balanced twisting method in the SilverCab cables results in a dramatically improved audio transfer, less distortion, widened 3D sound-stage and a quieter background. This added to the already excellent dynamic performance of the high purity silver conductors, enables the ultimate listening experience.
Look at by eBay listing that can show you the differences!
IPOD Line Out to 3.5mm Audiophile Silvercab Connector - (eBay item 270194408894 end time Dec-16-07 06:10:19 PST)
I would say the sound stages improves by 20 - 30% depending on your hearing sensitivity. I'm also willing to back that up!!