This is a debate I really struggle to understand. Card on the table, I am firmly in the digital (especially Ethernet) cables do not make a difference camp.
What I don't get is this:
People are convinced they hear a difference. I believe them - how could I do otherwise. They have conducted their 'test' and they hear the change. Others explain the engineering and say there can be no difference - look I can prove it. I believe them too.
Where is gets strange for me is that there are really only two possibilities here. The science is wrong (or incomplete) or there is no difference. Given that there is plenty of research on how our senses (and by extension our brain) can fool us completely and given that in non-hifi applications the question of cable quality (so long as standards are met) is irrelevant then I tend to side with the no difference brigade.
It is understandable (and science can and does explain this too) why people assume that more money = better and are quite willing to spend extra and convince themselves post purchase of the benefit - confirmation bias, it's interesting stuff.
This does not mean that the science should not be challenged - it might be wrong. There might be something going on that is unexplained that is peculiar to hi-fi data transmission and no other form of data. I would ask however, what is the likelihood of this?
I have been told before that this is a closed minded approach. Maybe, but is it not equally closed minded to shut out the possibility that it is our perception that shows a difference rather than the reality?
Finally - for those that 'hear a difference' and are happy with their purchases and the money they have spent. I am genuinely happy for you. I make my choices based on my experience and understanding and it is right and proper that you make yours based on your own experiences.