#because sam doesn't

DEAN: What I've been trying to say for months. It's time... time to stand down. SAM: You want to quit? What's happened to you, Dean? Ever since – DEAN: Ever since what? We lost pretty much everyone we've ever cared about? Ever since the Mark made Cas go crazy? Ever since I had to bury him in a Ma'lak box? Ever since then?

This. THIS?! is where they cut to Sam so the audience can see his reaction. Not THEY had to bury Cas in a malak box, Dean's literal nightmare, no. Ever since DEAN had to. Cut to Sam's reaction not to losing everyone they've ever cared about, no, but to finding out his brother had to do that to Cas.

Yeah. You know why? 'Cause the monsters – they're everywhere. Everywhere! What we do – it's not even Hunting anymore. It's whack-a-mole. We don't even save people. Every friend we've ever had is either dead, or they got wise and they packed it in. SAM: Jody's still fighting, and Bobby – DEAN: Bobby has a death wish, and you know it. And Jody – ever since what happened to Donna and the girls, she does, too. And after Eileen... so do you.

A list of people who have a death wish or gave up: Sam since he lost Eileen. A Canon Couple. AU!Bobby - no explanation, but he has lost Mary, twice. Jody - Since losing Donna and the Girls. Dean - Since losing Cas.

What is this scene if not a recognition of what Dean and Cas mean to each other? of the fact that Sam knows what Cas means to Dean? Sam has a bigger reaction to Cas than he does to Eileen. Do you understand how insane that is?

The scene is sandwiched btw two shots of the present - between where Dean may lose Cas & Dean's tree side purgatory confession.

It's sliding doors. It's present and future. Yes, it's a future that is impossible, it's Chuck's trick, it will never come to pass, but it is one that's supposed to make an audience feel something while seeing Dean and Cas come back together in real time. It's yet another parallel in an episode chock full of parallels.

If Sam loses Eileen he'll lose his hope. If Dean loses Cas he'll lose his hope. and Chuck isn't only showing Sam a future where they both have already lost, he's setting up a present to make that hopelessness come to pass.