Man, Ragnarok. You and I need to stop the long posts.
Let me be brief. Picture this: Bogrot is cleared out. Goblins WERE keeping troops there, but you cleared it out. Why would they let days go by and NOT send new patrols out to see why their troops didn't come home?
Random Encounters simulates chance of encountering something because in life you never know what you might run into each day. As you travel through the forest one day, you may encounter a deer that scampers off. Next day. Nothing. Next day, an Owlbear. Next two days, nothing.
Each day, as you're traveling, you should encounter new things if it's a living world. You shouldn't feel like it's a ghost town once you've killed all the baddies in a particular area.