Harsh sulfates aren't always bad, they can serve a purpose. For example, Sodium C14-16 olefin sulfonate is one of few sulfates that can remove cationic build-up. That's build-up from conditioners that remove cationic conditioning agents instead of silicones. If you have a sensitive scalp or hair that dries out easily you can dilute products with harsh surfactants to reduce their impact on your hair and scalp. That's because what's much more important than strength is concentration. A product that's 99% mild surfactant will have a devastating impact on your hair while a product with 1% harsh surfactant won't.