They do, as well as strange markings on the back of their necks. [He would crouch to make it easier for her to see the barcode on the back of his neck (he's bald so there's no hair to move back or anything) if he cared. As it is, she can glance up to try to find it on his neck looking up. Buuuut. He just keeps on his way]

They're useless for anything except to shame people and make them easier to kill.