As a southerner who has also pondered this, I think it's simply the basic nature of the menu and local nature of the employees. Food is basically just pre-made

As a southerner who has also pondered this, I think it's simply the basic nature of the menu and local nature of the employees. Food is basically just pre-made batter, eggs, potatoes, and processed meat; all of which holds well and only requires limited refrigeration. Staff is pretty basic crew: Cooks and customers can order directly at the register if waiter isn't available. Add to that a culture of staying open at all costs and there you go.