It'd be a bit weird if the world of Horizon: Zero Dawn was just littered with treasure chests. Levelling up and finding new crafting materials is an important part of the game's mechanic, but treasure chests don't really fit with a prehistoric/post-apocalyptic world filled with robots.
But a robot with a chest on its back? Sure, that works.
Guerilla Games spoke about the walking robotic treasure chest a little in a new video uploaded by Sony this morning. Mathijs De Jonge, Horizon's game director, noted that they were looking for "different opportunities for the player in terms of there should be an enemy or machine that has a lot of loot on them".
"The shellwalker is basically a walking treasure chest," he explained.
So amidst all of these possessed creatures, there's also the robotic version of the treasure chest from Discworld.
The video also showed off the Snapmaw, which for all intents and purposes is a crocodile. The player needed a challenge "in that environment", which makes sense.
But you can't have all those challenges without a suitable reward. And even though this might be a weird techno prehistoric post-apocalyptic setting, a walking treasure chest is still the main way to reward someone.