Many folks including engineers don’t understand all of the challenges. The first one that completely misses the point is the notion that after miles and miles of cable from the switching station, how is the last foot going to make a difference?
First of all, all the nasties that send high frequency hash back into the AC live IN YOUR HOUSE. Secondly, have you ever heard of a water filter. That last couple of inches can certainly make a difference.
If memory serves, the backplates use switch mode power supplies. They are famous for generating all manner of high frequency noise which can modulate with the signal. I use double shielded cables with mine to ensure the noise doesn’t find its way to other parts of the audio chain.