No, you don’t need that, Dean, but your brother does.
Dean placing the smulet right there, in this intimate moment they share in the car, after this intense day, shows me that he learned that the samulet was never about a god, nor was it a reminder for Dean that he loves Sam. No. It was his, but it was about them, it was about Sam as well. And when he sees Sam’s expression, this realization hits even deeper.