It is part of a category system - every category named after a person has "hidden" parent categories from the subcats of Category:Wikipedia categories named after people, so you are misled when say that it is not part of a category system.  It is incorrect to add other parent categories to a category named after a person because the articles within the category named after the person are not part of those parent categories.  For instance, Barack Obama is indeed the President of the United States, but his family is not. -