What are you getting so excited about, Dean?
Castiel is millions- hell, billions of years old. Dean’s entire existence is no more than a blip on the huge timeline of Cas’ life. Yet I don’t think that there’s anyone who has ever mattered to Cas as much as Dean.
Also, Cas is a hurricane in the form of a man. With a thought he could wipe every trace that Dean ever existed off the face of the Earth. And yet, one touch, one word from Dean makes him stand down during his anger (a la the Cupid in Sacrifice).
And for Dean, Cas is his best friend. Cas understands him and knows him (think Road Trip, “you did it for the right reasons”). Dean needs Cas. and not for his power, not as an angel. Dean needs his best friend.
That’s why I ship Destiel.