you wouldn't have your hand in your pocket already
Some people (me for one) walk around with their hands in their pockets as a course of habbit.
I could post a dozen pictures of me with my hands in my pocket. Its just the way I walk around, gun or no gun.
Like Paw Paw says, not many bandits expect an old man walking around with his hands in his pocket to be gripping his revolver. Puts surprise in your court.