The Saunterer would be surprised if Darwin knew the answer, which we take off the internet:

    The skin in the area around the genitals is very sensitive. Pubic hair can naturally reduce friction associated with the movements during sexual intercourse and other activities wherein chafing may occur.

    Pubic hair can also help stop bacteria and other microorganisms from entering the body. Specifically, it can help trap dirt and pathogens that may enter the body through the vagina or penis.