Readers can easily find an article about a broad topic (like the United States) but have more difficultly finding an article about a smaller or more specific topic—especially if they don't know the article's exact title. These less prominent articles are often found by editors searching a category.
The chance of an editor finding an article—and correspondingly editing it—improves if the correct category tags have been added. Eddie might do this himself. If you're starting a new article (or undertaking an edit of one), pay attention to the categories that similar articles have been placed in.
It doesn't matter if early categories aren't perfect. Even an approximate category can put an article into a position where an expert can apply the appropriate subcategories.