You're making jobs harder because now the one or two cashiers are having to call people from other departments while the self service assistant is standing there not able to serve anyone because 8 people in the queue are refusing to use it even with help. The store has the same amount of hours to give out regardless of if you are going to the self service or the tills If they all break down we aren't suddenly going to have 4 extra members of staff in, the single person who would be working on them would just be somewhere else. you're not going to make them decide against using machines. All you're doing is making everyone's job harder.