why fluency teaching won't be coming to a school near you

As the conception of learning and hence good teaching has gradually shifted from a “behaviorist” to a more “constructivist” view, in line with emerging research, many educators have developed their own personal views of what constitutes good practice.

source:
Teacher Evaluation: To Enhance Professional Practice
Charlotte Danielson & Thomas L. McGreal

There you have it.

Knowledge isn't a "behavior."

It's a "construction."

Fluency teaching comes straight out of behaviorism. (Rate of response: A Legacy for Teachers and Students from Skinner through Lindsey)