"And how come I've enjoyed 45 years listening....."
Enjoyment is a matter of personal taste; it is not a defining factor.
Longevity has no part in the equasion whatever.
Irish Travellers were singing newly composed folk songs of their own making right up to the disappearance of their singing tradition in the mid-seventies.
Acceptance, absorption into and adaptation by a community is what makes a folk song, not whether it has been around for a long time (like Rule Brittania, say.)
Jim Carroll