Bruce I’m sure that testing things in your own home is a very good way to test things for all the reasons you suggest. And I have.
The other point, however, is that if I am going to spend up to say £9000 on power cables, I want to know what they are actually doing. Take the Cardas Audio Clear Beyond Power XL. £4,230. Each. One of the claims about this cable is this:

“The Cardas Audio Clear Beyond Power XL in combination with the V12 Amplifier yielded one of those unforgettable, you-have-got-to-be-kidding-me moments an audiophile never forgets! The XL was easily 25% more detailed, produced a blacker background, was smoother than my already smooth reference, and captured timbral realism beyond my ability to describe in English“

25% more detailed? Well, that’s definitely going to be measurable. And audible.

But a null test shows no difference with the stock power cord which costs nothing.

If a manufacturer wants me to part with several months salary for something that they don’t wish to subject to objective measurement in the form of a double blind listening test with a good sample of ears, but still want to claim it makes things 25% more detailed ….blacker background….smoother sound…etc etc….then I’m afraid they don’t earn my trust. But somebody who actually pays for it specifically to rigorously test it does.

I trust my own ears. But for £9,000 for a metre or two of cable, I also like to have an objective assessment of what’s going on.

ROON Rock on an NUC across the systems
Sitting room: 218, DSP7200SE
Study: 218, Quad 303, Spendor BC1
Bedroom: Musical Fidelity A3CR, Chartwell LS3/5a
Various Sonos boxes in bathroom and spare rooms