While he’s too young to hunt, he’d stay at the room on his own if they knew it was safe. It isn’t long before they decide that’s not the best plan, and he starts to stick with Dean on hunts. The two brothers work together as an effortless team even with the size discrepancy.
Even after John vanishes into thin air and leaves them to fend for themselves, the world isn’t so bad as long as they stick together. After all, Dean needs someone to haul his ass out of trouble.