Having grown up around several of my Appalachian relatives, and having lived for 12 years at the foot of the Appalachians, I can tell you what is going on.
These folks know that many of the things they say are grammatically incorrect. But, they use the incorrect wording for Emphasis, with a bit of humor thrown in.
For instance, "Ain't no way. Never gonna happen."
Or, "Where the heck is she at?"
Or, " I am stumpified by this problem."
Or, "Don't never do that!"
Larry the Cable Guy, whom I can't stand, speaks like a normal person when he is not performing. But, just listen to his Hillbilly sayings when he is on stage or in movies.
Mannyrock