Is the supermarket setting vital to the story? Could the story have been set in a car wash? in a fast-food restaurant? in a business office?

THe supermarket is a microcosm of the conformist status quo masses. There is no overt sexuality, excitement or adolescent fun. This is why the girls stand out and act as character foils to the other customers. A business office would amount to ridiculous plot manipulation. A place frequented by young people would not have contrasted enough.