The question is what is the impact of lack of attention, it is hard to keep attention when the job is boring and if 5 minutes of lack of attention are critical than it might be a good idea to make the job less boring by gamifying it. Taking an action even simple as pressing a button makes people more alert, that's why Japanese train drivers for example must do some hand movement of sometimes say some word when they see a signal, apparently it keeps them more aware. I am not saying keeping those people pressing buttons in the lift was for security reasons but it could be a desired outcome which was later observed as useful and therefore the position was kept as is.