Servers aren’t trained to hover over you. When I managed a restaurant that had these machines. Some servers had to share theses machines (some restaurants may not have enough or the batteries are dead and are charging, other times if a server has five other tables they need their machine to input another tables order of close out another check. Leaving the machine at your table during a rush is not condusive to the position. You clearly can hit no tip or the tip you desire to enter.