I am put in mind of electricity. We wish to generate light but succeed mostly in generating heat.
About two years ago on another similar thread) I did get as far as posting the definition of folk music adopted by the (Oh! Heck, can I remember it?) World FOlk music congress in (maybe) 1954 and now I can't find it. THe problem seems to be that there are a lot of people who think that applying the definition and deciding that a song is not folk is somehow to denigrate the song. THis is not the case. A song is no more or less worthy simply because it is a folk song. But that is no reason to refuse to understand wht a folk song is.
The problem of shifting meaning is not limited to folk song. Many people believe, today, that a work means what most people think it means (so "infer" and "imply" are confused, and "refute" is used to mean "reject" not even "rebut"). Likewise grammar is assumed to be correct if in common use. Those of us who disagree are described (with, I think, pejorative intent) as "prescriptive".
I do not agree with this tendency. Surely it is important to be able to be sure of meaning - but to remeber that this need not limit what can be sung, heard, or enjoyed.