Why don’t supermarkets have windows?
The trick is very simple: supermarkets want to keep you detached from the outside world, so you can shop for longer. Without windows or clocks, you have no idea what time it is and what the weather is like outside. It could be raining or snowing, and you will have no idea about it, since the nice music and products around you keep you occupied. But also, windows are much more expensive, and stores prefer buying shelves that are way more useful to them.