so when tuning was developed, the solution to being able to play in all keys with ten fingers was to create fixed strings or pipes of 11 scale degrees, each one tuned to a pitch that was a compromise between all the various shades of pitch that scale degree could have. so for example the major third on the piano... E is a tolerable major third up from C and also a tolerable major second up from D, but not a beautiful third or second.

it would be annoying to add more strings or pipes for the other notes, since then you couldn't reach an octave with one hand using our tradition keyboard layout.

now that we have electronic keyboards, there is no reason to stick with the one-to-one key to pitch relationship. each degree (keyboard key) of the scale can have several tunings.

someone build it, dammit!