I agree with chris'nightbird'childs that

"it's [folk music] still considered more of a Sixties style than anything else, with visions of Joan Baez emoting in people's heads..."

IMO, the United States is a mass media driven nation and the mass media has defined 'folk' for the people as Joan Baez type music.

Since we 'Unitedstaters' are not known for being independent thinkers, we bought and continue to buy this definition of 'folk music'.

Speaking for myself, prior to reading Mudcat threads,
I thought folk music was the Joan Baez, Peter, Paul & Mary sounds and no more [no disrepect intended or deserved]..

Away from Mudcat, out in the real world, I still don't use 'folk' to refer to the type of music I now realize IS folk-Blues, early Jazz, Zydeco and the like...

The problem may be that there are so many different folk here in the USA- with different folklore and different folk cultures -that there were bound to be different opinions of what 'folk music' is.

Maybe that's why out of the kindness of our folkie hearts, we allowed the mass media to define what would be considered 'folk music'.

That way the store clerks would know where to display the recorded CDs in those mass media supported, chain stores...