Sweetened tunings. Why such an issue for pedal steel?

[Zumbilly(Murdoch)]

I have never ever been out of tune.
Having cloth ears is the secret

[Will C]

I'm so glad to hear Ken raises his plain 6 string with an extra pull. I found the effect particularly bad when playing the "3 up" inversion of a major chord, the G# would scream at me "I'm flat", not because it was flat, but because it sounded flat with those other notes ringing. I wasn't sure if it was cabinet drop or the effect of the other notes, but anyway I devised the extra pull to raise it just a gnat's when the A pedal goes down, and it sounds so much better. At least I'm in good company.

[Nick Bidmade]

The guitar is out of tune when it's tuned (if you see what I mean). Frets provide a 'tempered' tuning that sounds 'good enough' to our ears.
If you go onto the Peterson web site, you will see there are several different piano tunings that can be downloaded... so the piano ain't in tune either!
The mathematics of intervals is very interesting - I'll just go and put my anorak on