There are many reasons to eschew typical shampoo if you have naturally curly or wavy hair. Cleansing hair without a shampoo can give straight hair back its natural fullness and body, and maybe even a wavy texture that was being shampooed out. Most shampoos contain harsh, drying sulfates that are extremely damaging for curly hair (ammonium laureth sulfate, ammonium lauryl sulfate, sodium laureth sulfate, sodium lauryl sulfate, etc.). They are often foaming agents that make curly hair frizzy and uncooperative. Using conditioner, or another replacement such as baking soda in place of shampoo will cleanse the hair just as effectively without stripping it of moisture.