The reality is that no one is really sure what the purpose of pubic hair is. It certainly has nothing to do with temperature regulation, as some people believe. Most female mammals have some sort of visual clue that alerts the males of the species that they are undergoing estrus and thus fertile. Pubic hair is what is known as a secondary sex characteristic . It only develops during puberty, and thus may have served as a signal to males that a female was capable of conceiving.
Most animals secrete special scents that act as sexual attractors.
It is somewhat debatable whether humans respond to such scents, but we still seem to have the appropriate glands and receptors. It is therefore possible that pubic hair acts to trap these scents. Regardless, if you enjoy trimming your pubic hair, there is no reason not to. You can avoid itchiness by simply continuing to shave or trim. A little baby powder would also help prevent irritation from perspiration.