There are no such things as "zeros and ones". That's just a conventional way of referring to on and off states, and "digital" cables transmit an analogue of the digital signal, and as such the pulses have a rise and decay time. Look at how square waves are affected by so many factors. At least that is my understanding of it.
I get that, and I do try and keep an open mind (and open ears) with regard to everything, never mind cables.
The problem I have here in trying to understand how there can be audible differences is that the terminology between whether something is technically digital or analogue is irrelevant. Whether we consider the transfer of the 'digital' signal as being in an analogue state, and whether or not the waveform is an exact square wave, there comes a point in the chain when this signal is converted to 'true' anaolgue. In this process of conversion, the 'digital' signal is interpreted as being in either an on or off condition. There are no partial states. The digital to analogue converter 'reads' the input as either on or off. Whether you call the signal digital or analogue is not really important, it will still always be interpreted as being a change between solely two states and not any form of linear progression.
With this at the forefront, my 'problem' is that I cannot understand how a cable can have any effect on this process, other than introducing errors of such significance that they would stop it from working at all. I do and can understand (and believe) that a digital link can carry other surplus waveforms and frequencies that might have a direct effect on the analogue section of equipment down the chain. I can quite see how in this way an optical digital transfer could be beneficial. What I cannot get my head around (and I have to say, what I have never heard) is any repeatable, substantial differences caused by the type of wire carrying a digital signal.