why Polyphonic guitars?

remember the step from the mono to poly synthesizer? The step from the monophonic to polyphonic guitar is not quite the same but of a similar order:

Polyphonic distortion is most spread reason, because it exists since the 70'es, and the difference is brilliant, there is no intereference between strings.

Polyphonic Enveloppe
All effects which read or create an enveloppe work a lot better because for example a monophonic touch-wah filters all strings at once, independent on which string is plucked.

String Selection
Once separate string signals are available we can detect the loudest, lowest and highest playd, the last attacked... string and give it a different sound or mute the others or whatever...

GuitarSynthesizer
Once pitch can be detected on each string, a synthesizer can be driven.

some of the effects immediately sound better for any kind of playing
others allow to play new sounds with the old guitar technique
others need to be rehearsed, some need heavy musical skills...