Over last spring I had a problem with egg eating. It started with an occasional egg and quickly progressed to all the eggs. I believe it was stress induced by a bully cockerel I had with the girls at the time. For some reason he didn't like any of the black hens, which was more than half of them. Kinda odd since he was black himself, but who knows what goes on in those silly bird brains. Anyway, he was removed, but they continued to eat eggs. So I put some curtains on the nest boxes and presto, no more egg eating and still not to this day, many months later.I think that is the original purpose of curtains on nests.
But most of the time, it doesn't really matter, so I think it is mostly a crazy chicken lady thing.