All cables can only degrade. So with cables, you get degradation for impedance mismatch and signal degradation. The closer the cable adheres to the impedance spec (90 Ohm) the less impedance mismatch derived degradation. Equally, the lower the various losses in the cable (related to the amount of copper, plating, isolation, and geometry), the lower signal attenuation, and thus the signal level degradation. If either degradation becomes too large the USB signal is cut or unreliable, before obvious problems are noted (cut out, no connection) sound quality can still be affected. However, the regenerate/reclock/rebalance technology that we implement in our products can largely revert the degraded signal. Good cables simply cause less degradation to start with.