It stands to reason that we love chocolate cake because it is sweet. Guys go for girls like this because they are sexy. We adore babies because they're so cute. And, of course, we are amused by jokes because they are funny. This is all backwards. It is. And Darwin shows us why.
All that is not useful in a picture is detrimental. A work of art must be harmonious in its entirety; for superfluous details would, in the mind of the beholder, encroach upon the essential elements.