A shop has two audiences
Outside, someone stops at the window for three seconds. Inside, someone waits at the till with nothing to do. Those are two completely different ad surfaces — and if your screen sits right, you have both.
After closing time only the audience changes. If your window screen keeps running in the evening, it sells ad time in hours when your shop is otherwise dark.
Your own material stays on: sale, new stock, opening hours. It runs in the free time and costs you nothing. We only fill the slots in between.
Bookings often come from your own street. The café three doors down reaches people who are already out shopping.