Maybe some are inclined to be all scholarly about this.
Maybe it's a mix of geography (Atchafalaya, Honey Island, Congaree, Okeefenokee, Everglades, etc.) and/or the presence of gators, tupelo, cottonmouth, fire ants, the purple berries, etc), and/or the feel, the feel, the feel; the ritmos, the rhythms, strut and glide, the chanky chank, the thchopitoulas and tchfuncte, the stupefying heat; ima axe you a question - you gonna dance?
Tony Joe for sure (although listen, he was on the Pop Staples path), and Lowell George, some of the others mentioned above; my feel says it ain't got to do with rockabilly, nope, or some that other stuff above, but I ain't nothin, so what? Once upon I time, I lived in Louisiana, a stone's throw from the Tchefuncte.
Also, Gatemouth Brown, and south-of-I10-Sonny Landreth and the one and only Pops Staples:
('ol Carlos looks a little lost at the beginning of this but finds a little foothold, Gate brings it back and the horns!)
listen to that rhythm - that is whatumtalkin'bout