Nobody asked them, Jim, because the obsession with definitions is a recent phenomenon.

Errr.....not really - sorry but I can produce a hundred (well a large number anyway)of quotations showing just the opposite. Remember Cecil Sharp called his first book "Folk-Song, Some Conclusions". It was about amongst other things, definitions.

The problem is/was that people like Sharp "knew" what a folk-song was, so that was what they collected.

Child knew it didn't include broadside ballads for example.

But no, it isn't a recent phenomenon at all. Sorry and all that.