In Mystery Spot when Dean died 100 times, what if each time Death was the one who took him. What if they had a little bonding session every time he died and got closer but then Dean forgot everything when Gabriel set things right. What if that's why Death has a soft spot for Dean, because they were once bffs.
Can we all just take a second and look at Cas's real problem in his 'life'? He just wants to be loved, and he feels betrayed when the people who love him leave. God, Lucifer, Balthazar, Dean(well, he brought that one on himself.)