Why power cable effect overall syste sound?

Grant, Thank you for your informative comments.

I’ve never tried anything but stock power cords on any of my gear so not sure if they would improve things or not. But if I tried to figure it out from this thread, well…fuggettaboutit!
To me, this type of thread is exactly what cable manufacturers want. When this gets hotly debated, each side amps up even more. Instead of writing about subtle improvements you get people writing “I was shocked” and “My wife walked in the room and asked me what I did to my system” and “My non-believer buddy came over and his jaw hit the floor.” This has got to be gold to a manufacturer regardless of what the naysayers are writing.
We are talking about the AC from the wall fellas. If the cord changes that 50 or 60 cycle waveform then the manufacturers can figure out a way to show me that. I’ve read their websites, and believe me they can be very creative in their marketing. But go to the “Technical Specifications” (or similar) page of their sites and you get more marketing, no data, no proof, no before and after waveforms. Why not – It’s bad for business, that’s why. I’m not saying they can or can’t prove it, but whether or not a cord does anything and whether or not this can be proven will remain to be debated because the manufacturers have no reason to prove anything.
And btw – The reason why this thread has gotten so much attention is because the OP stated “Power cables effect the system sound. This is a well-known fact.”

The manufacturers had to give into the demand for detachable power cords to stay in business.I was told that some wanted to keep their hard wired cords but had no choice.The IEC connector used is disliked by many,including people that use aftermarket power cords.

There are also power cord builders that make a claim"UL APPROVED" that must not have any knowledge of the laws or products they are supplying.How could you trust them when they make a improper claim like this.Power cords are not "UL APPROVED".A popular company does this.

Knownothing, First of all I would like to say I have never said power cables don't make a difference. I have tried numerous power cords and I hear the difference in each and every power cord as I do with every speaker wire and interconnect. System resolution would have to be at an all time low not to hear the difference. What I am saying is I prefer the sound of the original power cord. Maybe I have a purist attitude in this respect and obviously I am not alone. If a given system does not sound right I simply look elsewhere.
I have tried after market power cords on all types of equipment. I was only using amplifiers as an example because of the extreme differences in the power cords of the two amplifiers I mentioned and to make my point.
I understand this thread began with "Why power cables effect system sound", but it evolved rather quickly.
Power cords are not the only thing up for debate these days. I recently spoke with two well known amplifier and preamp designer/manufacturers in a discussion about speaker wire and interconnects. Both said they did not take speaker wire that seriously and they felt the interconnect was much more important. Personally I have had a change in speaker wire make or break a system. However, I respected their opinion and it gave me something to think about when one of them said the most important thing for speaker wire is that it is efficient since it is tranfering the power.
In this hobby there is no right or wrong and there is no such thing as a perfect system. What we believe today we may find out is wrong tomorrow. The main thing is that we enjoy the music along the way. Isn't that how we got into this in the first place?