Mine get pets in the morning before they leave the coop and every night, before the lights go off. Crazy as it sounds, if standing there and they have eaten their fill (being that they load up just before bed), they get up on the roost and line up to get pets. I think the key has been that they are handled and make physical contact with us every day since we got them. In the better weather, if we are sitting in lawn chairs some will jump up on the leg and settle down to get pets and after awhile, jump back on the ground. Then another jumps up and the process repeats. About half do this.
I am thinking it is in the consistency...we never let off as time or circumstances change. I would encourage this if you want this kind of contact. Can't hurt. jmho