Because clay is very inexpensive and no one is going to make a big profit on it. Even in the alternative health world people try to get as much money as they can. People usually would much rather sell something that is going to make them good money but might still be effective than something that is very effective but won't make them much money. It's all just business. From all the experience I have with natural ways of healing I've found that usually the most simple and inexpensive things are the most effective.