If this is such a powerful tool, why is it so few people have been taught it?

Talk to doc. Most of the forces in our lives, from our parents to our teachers, to our army sergeants to our spouses or the irs - are much more interested in having us satisfy their needs and live up to their expectations than they are in setting us free to be who we really are. The notion of increasing the healing response is a new one to mainstream medicine. But all major institutions are now using it.