Well, the use case is generating a month's worth of pages, one for each day, all with the same template and in the same category, "day" (it's for a course website). I did this manually a month or so ago, but may need to re-do it if I'm assigned to teach at a different time (my assignment this summer might get switched, and some day I might teach again).
I can imagine other uses, like starting an encyclopedic wiki, and building it on some pre-existing classification rules. For example, I just saw recently that a professor/blogger at one point wanted to use JEL codes, of which there are hundreds, to organize articles on topics in economics.
EDIT: Oh, I could try out the API, too.