Why the three characteristics not included in Satipatthana Sutta?

Why are the three marks (consolidated) not directly included in the Satipatthana Sutta - supposedly the most important of all discourses? Not in the section of principles, but indirectly with regards to the body: > *They meditate observing the body as liable to originate, as liable to vanish, and as liable to both originate and vanish.* Perhaps it is due to the later historical ontological organization of those three messages? Any tangential ideas are welcome.