This is surely a 'chicken and egg' chronology issue. Folk music (in England at least) was defined mainly by 'teachers' so it is no surprise that what is generally thought of as folk music nowadays attracts those who invented it in the first place.
Real folk music - if there is such a thing - was/is often far removed from that preserved (probably by teachers) at the EFDSS and the BBC.
(This is not to say, incidentally, that this is not good stuff - its just that it is only part of the story)
The music I heard as a youngster, sung by good old boys in pubs in remote parts of East Anglia in the 60s/70s, included music hall songs('Oh Joe the boat is going over' and 'Tarpaulin Jacket'), crude ditties and even contemporary pop songs ('The Glory of Love', I remember was a particular favourite). There weren't any teachers around to say whether it was folk music or not - although there were a few engineers joining in lustily on choruses:-)