He want to.
Damn it, he does but he's learned.
Angels are inexperienced with emotions. They weren't necessary, as the angels were meant to be perfect soldiers ( And Castiel was the quintessential soldier.) They're confusing to say the least. But Castiel's become very familiar with them during his time with the Winchesters. At least, he knows enough to form his own opinions and he's decided he doesn't like pain.
And seeing Dean smile at that...that woman, so normal and human and happy-that's painful, like knives and angel blades buried just below the skin, just out of reach.
He wants to see him. He wants to talk to him. He wants to...He doesn't want to want to.
But when it comes to that particular mortal, he's also learned that he doesn't have a choice on how to feel.
I wrote this before watching season six. This was my take on why Castiel never visited Dean. I seem to be inching away from fanfictions and toward writing fictional stories. Huh. You think you know yourself. ( I'm sitting here watching Katt Williams and rolling on the floor laughing. Lol.) Don't worry, I won't stop fanfictioning. I couldn't if I wanted to, and I don't want to. I just hafta say though, I've been watching Daredevil for a bit, already on the second season, and there is nothing you could say to convince me that they only like each other platonically . Matt doesn't smile at him like a friend. HONESTLY. I almost melted just looking at that smile.