[ It sounds simple when Dean puts it that way, and for Dean, it must be. He lives alone, operates independently from those closest to him. He doesn't take orders from or work to protect his family, and so his decisions are truly his own. Castiel doesn't have that burden of responsibility. It's something he couldn't possibly understand, and so Castiel doesn't defend himself or try to explain. He listens to Dean's frustration with his head bent, and as he considers his own predicament and the answer to Dean's questions, he presses the tweezers in again, digging for the bullet he'd been so close to retrieving before he was interrupted earlier.

It's not until the bullet is caught and plucked out of the wound in a renewed gush of blood which Castiel is quick to pressed a bandage down on that he answers. ]

I told you earlier. You've been chosen by God for a higher purpose, and I was one of many sent to retrieve you. ...I had expected you to already have been called to that higher cause, but I see now that I was mistaken. You need instruction, still. Guidance. You have no idea what you're capable of.

[ He drops the bullet and tweezers both in the first-aid kit, presses the end of a roll of bandages to Dean's thigh, lifts his leg, begins wrapping while holding the first pad in place. ]