Well if you want to get into it....
CAbLeS Ar3 PlAcbO... jokes.
I have experienced lower impedance cables opening up the sound of an iem more, and that makes sense from a scientific stand point. Beyond that they really are placebo imo and audiophiles seem to love kidding themselves their pixie dust infused unicorn hair braid really does make the highs sparkle more.
It's amazing that people continue to beat this dead horse despite an entire industry and profession that will tell them they're deluding themselves and back it up with evidence.