Why aren't they bugged by flying insects?

If I leave a door or unscreened window open for any length of time, I’m going to have some fly or moth coming in that drives me nuts.

Yet supermarkets and drugstores and medical offices and other places that leave their doors standing open or else have them constantly opening and closing do not seem to have this problem. Why? Why aren’t there moths buzzing around the lights in the produce section, or flies in the meat department?

Not that I want to see them there, but how come, anyway?

I even have neighbors who leave an unscreened front door open in pleasant weather. They don’t seem to have crane flies flitting around their walls.

I do remember that some birds nested in the beams of a downtown supermarket once upon a time, and the store guys had a terrible time getting rid of them. Droppings were a problem. It made me wonder why that doesn’t happen more often.

I seldom see pests or vermin of any kind in places I visit—and that’s a good thing!—but it doesn’t seem right that flying insects hang around my door looking for opportunity when they pass up much bigger opportunities elsewhere.