Who says cables don't make a difference?

I play the guitar myself, and cables would not have the same relevance there that they do in home audio. With home audio, we are placing cables after the source and changing that sound. With a guitar, most of  the processing of the sound happens after the cable, in the amp, which then modifies the signal it receives from the pickups, and guitar amps have a lot of tone control over the sound, much more so than any cable does. So you really can not compare the two in the same discussion. When I play, I dial in the sound I want with the controls on the amp, a cable placed before the amp does its thing would not have great affect, and what it does have would be just one setting, and easily modified to a much greater extent by my manipulation of the different tone controls. Cables, and individual pieces of equipment are our tone controls in home audio. I am still unclear why it’s such a bad thing to have those in our hobby, though I believe feel that it impacts the sound in a negative with with active controls?

Cables, and individual pieces of equipment are our tone controls in home audio

I would disagree with this statement.  Tone control is too broad an analogy.  

The subject is broad. Most equipment has its own sound. It imparts that sound into what you hear, but you only have have sound for each piece for the most part. Some equipment does have the ability to select some different sounds. People buy audio equipment all the time because of the sound it gives them in their system. There’s no doubt about that. With a guitar amp, while each can ha e a totally different sound, they offer way more range of sounds and tones that they can create. Of course that’s because their purpose is different, they’re intended to create using, not reproduce it. I know many are against tone controls, etc on audio equipment, but personally I don’t see why, as long as that doesn’t take away anything. 

While there could be a difference, there is some bad physics used to sell some cables. For instance, skin effect and the claim to need to mitigate it with litz or ribbon construction. Skin effect is alleged to increase the resistance of speaker cables by diminishing the cross sectional ares of the cable conducting the signal. All this is true, but how much does the signal get attenuated by the increased resistance at 20 kHz? This can be calculated and approximated within a few percent by multiplying the skin depth by the outer circumference of the cross section. For typical 8 gauge cables ten feet the effective resistance changes from about 0.0064 Ohms to 0.011 Ohms. Put this in series with 4 Ohms such as a Magnepan speaker and the ratio of resistance is an increase on the order of about 0.01 db. Skin effect is not an issue and cable designers either know this or they ought to know the engineering/physics to calculate it. This issue destroys the credibility of so many of their other claims such as confusing grain boundaries with Johnson-Niquest thermal noise of any conductor and the insulation introducing electric field distortion from dipole molecules in the insulation.
I do not question the possibility of a badly constructed distorting the signal but I do not believe thousands of dollars or even hundreds of dollars for a cable can pass a strictly conducted double-blind test over a well constructed cable. Could anybody whose ego is connected with spending $12,000 admit they hear no difference they don't imagine? I am not so sure.

@drbarney1 , you really should have thrown in dielectric diffraction and triboelectric effect in there for good measure?  ... I am laughing with you, not at you.  I probably shouldn't tell you I once read a "respected" audiophile claim you shouldn't use speaker wire much bigger than 10awg because the effects of skin resistance get too large? ... ya, shook my head at that one too. Surface area is obviously too complex a concept for some people.