Why are Wilderness Encounters more Numerous?

What is the reason behind the Wilderness Encounter numbers of many monsters being much more numerous than the dungeon encounters? I can understand this for large monster camps in the wilderness, but why are, say, goblin patrols more numerous in the wild compared to teh dungeon?

Because the goblins think to themselves, “Encounters in the wilderness are really dangerous! We’d better form into larger groups.”

(I know that sounds circular, but it’s not. The risk of encountering unexpected high level monsters in the wilderness is real, and therefore makes the wilderness dangerous regardless of the size of goblin patrols. The larger goblin patrols are a response to the wandering wyverns and lion prides.)

I understand. So humanoids go around in large groups in the wilderness for the sake of safety (especially in my setting - they might encounter a T-Rex!).