Most Helpful Guy
I think he wants to make the move, but maybe your just not giving enough signals for him to tell him your interested. He's probably afraid of rejection. He probably doesn't know how to interpret a smile from you? he could think your smiling because you are being friendly and polite, but not necessarily interested.
He could also be shy, shy people get easily intimidated, I am very shy myself when it comes to pretty girls, I find it hard to talk to them or knowing what to say to them, a shy person won''t ask you out unless he 100% confident you like them., its very hard for a shy person to make a move.
Its either one of those two things, that might be holding him back from asking you out.