One main difference between the two is fragrance. The fragrance in men's shampoo appeals to men more in a holistic and aromatherapy way. Many men are turned off by the smell of coconut, flowers, passion fruit, etc., so they do not want to use those for cleansing the hair and body.  How marketing does play a great part in selling men's shampoo versus women's shampoo, there are a few different reason's how men's shampoo are different than women's.