I've never seen one except in old movies and I do mean old. Apparently, in the early days of motoring, in the 1930s, there were roadside places to eat that were completely open, essentially an open-air lunch counter. I don't know that such places ever actually existed but I doubt they would have shown up in a movie if the didn't. They seem like something more suited to southern climes. They may not have been at all common but I can remember an institution referred to as "tourist cabins," which were exactly what they sound like, about two steps below a run-down motel.