To try it out. It's ruler functions sound amazingly useful for background work; I figured that kind of thing was something one would wish for but would never actually get. Honestly haven't tried it yet, though, so it might not be as amazing as I'm hoping for.
Fun fact: in Japan, Manga Studio is called "Comic Studio," because manga is a word in Japanese that means comic. Despite the name, it seems like a useful tool. John Allison uses it, after all, and he's never, ever wrong.