You're not going to flying the ship using the viewscreen, you're going to use your console. So as long as the visitor isn't sitting in your lap then you should be fine.
Good point. It did seem like that's how it was played though - especially the helmsman during a battle or other tense situation. He/she always seemed to watch the main viewer, look down and tap some buttons when they got an order, then watch the viewer again to see what happened.
About the only time they really did ignore the viewer was when <plot device> made the viewer useless, or they were told to set course for some place that would take hours to get to.