I think the Navigator's are delivered daily to allow for changes in the schedule. On the repo cruise last August, we had first-hand experience with this.
Due to Hurricane Hillary in the Pacific Ocean, we had to skip Cabo San Lucas and substitute a day at sea. The next morning we had a Navigator titled "Welcome to Manzillo" as Plan B went into effect. They had quickly assembled all the information we needed to plan shore excursions, and still had many shipboard activities from which to choose.
Preparing and giving them out a week at a time could cause lots of confusion as changes and updates were needed...