Usage of Dividers

Do any of you who run register get customers who stand there with a deer-in-headlights expression and will not, even with dividers, unload anything unto the belt until the customer before them is completely finished and gone? Or better yet, the ones who wait until everything has been rung and up and the customer ahead of them is paying, then put a divider down and start unloading - OK, thanks, now I clearly know that your items are not to be rung up along with the empty space on the belt in front of them.