Pancakes and eggs

What makes pancakes and eggs morning food? Why is it that if one serves pancakes or eggs or french toast for supper we call it "breakfast for supper?" As though our efforts to make the best of the only things left in the kitchen (too many eggs, flour and 6-month-old syrup) are somehow deviant, and so we must call out the exception. I've never heard of "supper for breakfast," but I suppose we do make note of pizza being eaten cold when it replaces our usual cereal or toast.