Is it important for managers to be qualified as managers?

It is difficult for most of us to imagine anyone attempting to practice law or medicine without some form of education. We cannot begin to think of the problems generated by firefighters or police officers attempting to fulfill community responsibilities without completing some form of training program. With the finest business schools in the world in the United States, and the most competent professional associations and societies on the planet, why in the world would we work for managers who have no formal education or training, and all there experience is gain through on the job training. In the United States, is it important for managers to be qualified as managers?