Well, yes these not true dedicated line in the sense of providing your own independent ac line, even a line run from pole wouldn't be truly dedicated as sharing with everyone else on that trunk line.
@richopp takes this thing to extreme, funny! But yeah, we'd have to go to extremes to eliminate all noise on ac lines. Some, I included, have tried batteries for provision of audio power, but even this has limitations in the sense of noisy inverters.