We might as well question certain assumptions that have been around that long. A good way to start is refretting guitars. Standard guitars are fretted to 12 tones per octave, conforming exactly to the keyboard of the piano or organ. Because it's the simplest and Icheapest way of tuning an instrument to fixed pitches that will produce any worthwhile music. They also use bottleneck sliders to get pitches between the frets.
Some synthesizers make provision for bending tones.
So the desire is there. We can do this by yanking out the old frets and installing new ones. Well that depends. Now there are enough possibilities to go around. These can all be done on guitars by changing the frets, since I have compiled fretting tables.