Using the 1954 definition results in football chants becoming folk songs. I am not saying the definition is faulty and, as Steve pointed out, it does help academics study the genre. As far as I can see though it does nothing to help potential folk club audiences to decide who to go and watch!

If Ed Sheeran performs "The Parting Glass" is it folk?
If Martin Carthy performs "Rave on" is it folk?

There are too many corner cases and exceptions for me to help define it!