Stim - you're missing the point. "Folk songs being created out of the entertainment industry" is something that happened quite a lot between about 1850 and 1900. 1900-1950, not so much; after that, hardly at all. And before 1850 there were songs, but there wasn't so much of an entertainment industry.

Life in Britain changed out of all recognition between 1800 and 1900, and what we now think of as folk songs are a product of that history. You're mistaking a historical fact for a general law.