Light always creates a shadow. You can't have only light. It would be like having only sound, with no silence. It would be very dull after a few moments. People like variety. But they forget about that when it comes to the topic of good and evil. If you really forced everyone to be good 100% of the time they would rebel and kill you so they could go have a beer or whatever.
People really don't think about this as much as they thiink they do. Even the "spiritual" ones.