Technically, it does.
There's a specific classification authority that usually resides at a command level, and is based on precedence and threat analysis. They determine the specific criteria for classification of categories of information, which is then documented into classification guides. All the other classification is then derived from these original classification instructions.
However, lots of people mismark their documents, or don't take any care in creating them, which leads to over-classification, which makes the declassification process take longer, since the people with the declassification authority are generally busy with other important matters, they're not likely to spend the time needed to go through a document and review it carefully for information. They're reluctant to do so lightly, because essentially if they miss something, they run the risk of creating spillage, which would be bad.