Their locations. We have one in the little town we live in, and it was the only decent sub shop in 20 miles.
Till the local gas station chain Casey’s put in an expanded food line. They now have great pizza (3rd largest pizza chain in the US) and good subs. Subway has a lot of competition.
I wonder if pizza quality varies between different Casey’s stores. We picked up pizzas there for the first time and even my teenage boys didn’t eat a lot-they normally eat huge amounts of food. All the kids said it was too greasy, pizzas were sitting in a pool of oil.