I think that there might be a deeper cultural link between Folkies and facial hair.
The more traditional folkie is very concerned with the idea of "authenticity".
They feel that there was somewhere, sometime a pure seam of folk song, untainted by music hall, popular commercial music etc.
In the same way that the Metal Kids or the Goths use their appearance to indicate their allegiance to their chosen sub culture, the adoption of the bearded look indicates an attachment to previous times and fashions.
While in Worcester's Guildhall yesterday, I was looking at the portraits of the previous Mayors- all hirsute prior to about 1880!
A preference for "real ale" is another quest for authenticity, and the use of a pewter tankard (with a glass bottom so you don't get nabbed by the press gang!) is another indicator of an adoption of the habits of an earlier era.
As far as I know, there are only two music genre subcultures in which adults, as opposed to adolescents, express their musical preferences by dressing up and adopting a certain lifestyle. Those are Folk and Country.
I could describe Line dancers- but that is Anthropology- the study of an alien and possibly incomprehensible society!
Cheers
Dave