The idea of folk music arose from people noticing that the music moving in oral tradition was largely a different thing from the music in the professional music tradition, and the observation of that reality wasn't contingent on preferring folk music over non-folk music or vice-versa.

For instance, "Hop Joint" is considered a folk song because John Hurt learned it from a friend for fun in about 1902 and we don't know of any professional musicians performing "Hop Joint" earlier than that, and "In The Good Old Summertime" is considered a non-folk song from 1902 because we think Ren Shields and George Evans actually wrote it and didn't lift it from oral tradition. Of course, that is not defining "Hop Joint" or "In The Good Old Summertime" as folk music based on how much anyone gets excited by each song.