well, I see your point about this film...I also wondered why there were more "popular" singers in the soundtrack. But Iris Dement appears in the film and sings and she is not what I would call a folk popstar, exactly...

They could have gotten non-traditional singers to sing this stuff, but they didn't. Can you imagine the soundtrack of this film with Jewel, Sarah Maclachlan, Ani Difranco, etc.?