Those who can, do. Those who can't, teach and many develop a leaning towards folk music. Is it "a lesson too late for the learning"???
I'm only joking.
Perhaps the intellectualisation of folk music is responsible for this and there again, perhaps not. How many traditional singers and musicians were teachers? I don't know but what they have passed on has taught us a lot. Could that be a connection? All depends on what your definition of a teacher is.
Furthermore, how many teachers have left the profession and become professional folk singers? I bet you can all name one.
Bob Fox tob start with.