Having lived in the south for a few years, I was amazed when the day arrived that I seemed to be able to comfortably say "y'all" (without wincing). The problem with filmmakers is that they seem to think there is only one type of southern accent.  It varies greatly within the region.  Interestingly, it has been noted by linguists that the south midland dialect of American English has retained more elements of Elizabethan English spoken in the time of Shakespeare, than even modern British English has retained.