Two-channel Stereo sound can be provided by two Mono cables, or a single Stereo cable.
What differences, whether significant or not, are there between pairing each voltage lead with its own ground lead versus sharing a single ground lead between [an arbitrarily large number of] audio channels?
Below I include details of my thoughts that raised the question.
Mono cables each transmit one channel and each have two leads: voltage and ground. Using mono cables, the number of channels (N) can be increased arbitrarily by using a matching number of N Mono cables, for a total of 2N leads.
Each Stereo cable can by itself provide two audio channels with only three leads: voltage L, voltage R, and a single ground lead (shared between channels L and R), effectively providing the same throughput with one less lead than the Mono configuration, which makes me wonder what [functionally inconsequential] differences there are between 1 x Stereo quality vs 2 x Mono quality.
Furthermore, 4-lead cables (such as stereo headphones + mic over a single bus) provide 3 channels using 4 leads: voltage L, voltage R, voltage M (mic), and one single ground lead shared by all three channels!
Assuming there is no quality loss when channels share a ground lead, then a Mono-only multi-channel configuration wastes half its leads save one (N-1).