Joe-
That's epistimological nihilism! THe fact that people misuse existing definitions instead of creating new ones for things that don't really fit the original definition (like "folk") doesn't mean that it's impossible to develop a useful definition. Or that such a definition isn't useful.

An analogy: What's the definition of a car? Well one could quibble about whether or not it has to have four wheels,or whether it must be powered by an internal-combustion engine, or whether it must operate on public roads; deciding to exclude Fords from that simply defined class because one doesn't happen to like Fords is plain semantic balderdash (also poppycock and tommyrot).