Shampoos' pH is around pH 6.0, whereas soaps' pH is higher. After shampooing with products out of the right pH range, the hair cuticle doesn't lie down. This can lead to abrasion between the hairs, causing hair damage. Once damaged, hair is hard to repair, even with the most intense conditioners. Also,washing the hair with soap results in an insoluble build-up that is hard to rinse, leaving hair dull and crunchy.