There is no "traditional folk music". There are, however, plenty of traditional folk musics. Lots of different countries and regions have them - and guess what? They don't all sound the same! They're not a single genre! I presume, JohnP, you play a couple of them, perhaps from the UK/US traditions, rather than from, say, the Mongolian or Uzbekistani or Malian traditions? Personally I'm a huge fan of traditional folk musics from India, Pakistan, North Africa and the Middle East. None of them sound much like Dock Boggs or Lizzie Higgins, f'rinstance, much as I love the music of those two individuals. I guess that's not what you mean when you describe traditional music as a "genre"?

Marketing people realize that the same customers who buy Dock Boggs and Lizzie Higgins are a likely market for Asik Veysel or Gnawa drumming, so in their terms they are in the same genre. If you want to hear some Asik Veysel on the radio you're more likely to hear him on a programme that also features Lizzie Higgins than one featuring Atomic Kitten or Eddi Reader.

And people who like to understand what the music they're listening to actually means will use the same sort of reasoning on it for Asik Veysel and Dock Boggs (both came from cultural and religious backgrounds that influenced what they did in ways that nobody in a professionalized commercial form of music-making would ever experience).

The interesting thing about the sort of pop-and-rock-gone-feral that Jerry started off this thread with is that it ends up being an utterly different genre in practical terms. Where would you hear a bunch of geezers playing Buddy Holly for fun? Except in their homes, probably nowhere. You can't buy their performances on CD, they don't get played on the radio. You need the approach of an ethnomusicologist to locate that music at all unless you happen to be their neighbours. As a genre, it relates more closely to the corroboree music of the Australian Aborigines than it does to Springsteen in a plastic box or Beyonce from iTunes. (YouTube has made that sort of music-making a bit more public, but not much).