Of course, most teachers were once successful editors of the mechanics of the language in school, and when they found out that they had a talent like their teacher as editors of language, they decided to become teachers themselves.
Not having the capacity or inclination to understand Krashen, and probably never having heard of his work, and not having to have done so because Curtain (and the textbooks she fronts to the public) say this and Met says that, the boring beat goes on, with the dollars flowing into the coffers of the book companies and so everybody is happy.