When concepts lack meaning, as mathematics does, it is literally alien to our nature. You will find students writing essays on the subject. You will probably find the student cowering in the fetal position. If students enjoy math, they will learn math. Such ideas often get too blown out of proportion.
IMP works for some students, it fails for others, and it is closely tied to learning styles.
Many districts are blinded by its apparent success. Students who succeeded in traditional classes find IMP to be lacking. No college I ever heard of use IMP style programs in their lecture halls. No SAT questions involve pigs or pendulums. Making math fun is not the same as making math understandable in the real world.