They don't all read the book to learn the rules, but in general, the hens are looking for a safe hidden place to lay the eggs where predators will have a harder time finding the eggs or the hen if she decides to go broody on them. Most, not all, generally believe darker is safer. My nest boxes are not in the darkest corner of the coop, but the insides of the nest boxes are darker than any other place in the coop.