The main reason that we tune is so that we will be able to play an instrument with another instrumentalist and not cause rioting or the throwing of tomatoes. Perhaps we might go back to the way things were before J.S. Bach wrote "The Well Tempered Clavier" when the (so-called) black keys were 2 separate notes! In the olden days, the ones on the piano which we call "white keys" were back then the black ones. And the ones we call "black" . . .
ah, but that's another argument entirely!
Actually, I believe that the piano I was raised with was definately NOT tuned to equal temperament! It was so "sweet-tuned" (or rather, not tuned) that going up an octave was more like going up a minor 7th!! Middle C was closer to Bb. O-W-OUCH!! Many, many moons ago, when merely a slip of a girl, & I was in the Far East, I discovered that I could hear those darn "semi-tones" which are not supposed to be there. Then when I ran into some Polynesian guys with guitars & ukes, & their singing included some of those same darn "semi-tones." I was humming along with them, cause I didn't know the Polynesian words then, and they asked me how I knew the tunes. I had no answer for them. But I hummed along, nevertheless! They told me that the songs were some of the oldest ones that the elders remembered, and they had never met someone who was not from the Islands or mid/far east who could hear those notes. They said they thought that I was someone who had lived there (Polynesia/Hawaii) in a previous life! I said, "Can I go back there, & then? 'Cause that's the most beautiful music I have ever heard!" Funny thing is, a man sitting at a table in a street in the Far East told me I had lived in the Far East before, too! hmmmmm. . .)