Not "quite" right Dick. When used with downward deflection they add camber and adding camber allows the wing to reach a higher lift coefficient before stalling so technically they do add lift. But I have to agree that a lower wing loading is better all around.

In the end it's also about adding drag if the goal is to steepen the approach glide. Adding lift does this but so does killing lift with upward deflection and thus requireing a higher angle of attack to restore the lift that was dumped.