Cable directionality

I'm sure this has been discussed before but I missed it, so what is all this stuff with the direction of voltage flow with cables? Every cable you see any more has a little arrow on it. Since the signal is AC and travels one direction as much as it travels the other, what difference could this possibly make. I have talked to numerous co-workers (all electrical engineers) and they ALL say this is the biggest bunch of bunk they have ever seen. Since I am the only "Audiophile", I try to keep an open mind(I'm also the odd man out being mechanical.) Skin effect, resistance, capacitance, etc. are true issues. You pass power through a wire and it creates a magnetic field. You do deal with impedence and synergy with the driving source. How about a few technical answers from the audiophile community.