When will we ever hear turntables demoed fairly?

It's unlikely that you ever will hear an in-store demo that's completely "fair" and this isn't necessarily due to either incompetence or unscrupulous behavior on the dealer's part.

Frequently, confirmation bias sets in, and the dealer doesn't pay as much attention to a setup he doesn't prefer.

Dialing in something like azimuth (on arms capable of it) can't be done by the "numbers" - even if you use the Feickert software, so there's a bit of subjectivity in this area as well.

If you're looking at an arm or a cartridge (not a complete setup), it gets trickier still, as the turntable's attributes can influence the results.  The best example I can point to is when I was developing the new Galibier drive system. 

During the early prototyping stages, I plugged in a Kuzma 4Point and Dynavector xV1S and the sound was overly aggressive.  The Kuzma was new to me at the time, so I didn't have a good handle on its attributes.  By the time the drive system was production-ready the Kuzma's attributes began to show and what was previously aggressive, was now a sweet, extended  treble.

Cheers,
Thom @ Galibier Design

At this level many prefer other cartridges in different arms. Most often I see Koetsu, Allnic, Air Tight and Lyra.

45 years back there wasn't any hype of playing with arms/headshells and other turntable tweaks.
there was only one standard turntable with stock arm that's it.
there was broadcast turntables that had capability of swapping arms mostly from Shure Brothers.
as to fair demo there won't be any no matter how 'proper' it's demoed. you're listening to the combination of arm/deck and cartridge. on decks with headshell standard mount arms you can simply swap headshells pretty quick to a/b between cartridges, but that's about it.
still not sure whatchya'll talkin'bout.

Everyday i demo my turnable fairly.

Here's the point of my original statement.That reviews are essentially nonsense,hyperbolic drivel that is designed to really do one thing.Keep the hamster on the wheel(that's you).If technical data were the sole criteria we wouldn't have this highly variable mess of designs.But it's not because there is an aesthetic injected into designs.Well tempered turntables vs technics direct drives just to name one large differential in design.Add the impossibility of fair AB comparisons and it's just a hot mess of cash flying every opinionated which way.Just one man's opinion.