Perhaps Ubi studied animal behavior and placed them in areas they felt they’d exist in the made up world? Animals do live in groups and defend territories. If the animals were sprinkled everywhere on the map the game would be way more difficult.
The crafting doesn’t really affect beating the game (story) that much. Maybe that's why it's do it and its done forever. I beat 3 again the other day hardly crafting anything. I get the feeling you enjoy a more immersive experience. For me more time fucking shit up and less time in menu(s) / talking to NPC's / crafting / etc. is ideal. Maybe 4 will be better balanced and offer more options?
Should be what the fucking about a man that carries a rook sack, everything he's crafted, 4 guns with full ammo, 4 types of explosives fully stocked, health, consumables, ancient knives, etc... then runs around full gait jumping up and zip lining down mountains and towers carrying all that shit. After that any type of reality goes out the window.