I normally use the kiosk for my luggage so don't pick them up to put on there. They're normally walking on the scale in order to get my tags from the back of the machine. Those that I do have to see an agent for I've never been asked to put them on the scale either. It seems the only persons that would get hit are those who put them up there without being asked, since again I've never seen an agent require that they be put on the scale. (At least on NW) Again those I've seen and myself might be lucky, but it seems like unless you decide to put them on there they don't ask.