Because being Valedictorian is mean to be a mark of highest academic achievement, not a mark of who is the craftiest asshole.
Sure, those students played the game. But they didn't win. Because the people that they maneuvered around are still better positioned in college. In my anecdote, for example, the valedictorian completed a bachelors in the same time it took the salutatorian to graduate and get through half their PHD at a top program. Basically, the valedictorian ended up taking twice the usual time to graduate.
Karma in action.