"OK, Glueman, I note you still haven't answered my questions"

It's not evasion, I'd have thought the difference between a live performance and a recording is self evident. The things the performer puts of her/himself into the material in 'real time' are what compels me.
I don't see it as an exposition of an old tune so much as an interpretation, a new voice meeting traditional material. As a rule I'd say a typical folk performance is fairly derivative and doesn't take a song as far as it might, it tends to be a performer's idea of what a folk revival song should sound like to a folk revival audience rather than a blank canvas taking the material into new places. That's a generalisation of course, some performers sound as though they are singing something for the very first time and make the hairs on your neck stand up, others make it sound like a school lesson