K-12 teaching is a low-status profession in this country, and in academia, teaching (what is already known) is less highly valued than research (expanding what is known). Teaching teachers is then the lowest of the low, totem pole-wise.
American attitudes toward teachers are frankly incoherent. We want outstanding people to enter the field but provide little incentive to do so. We expect teachers to be able to educate every child, including one for whom the obstacles to learning originate outside the school. They should be able to do this without adequate training, having figured it out on their own.