Why is the pubic hair curl?

When you're a kid you have a finer hair called vellus hair covering your pubis but when you hit puberty you grow a thicker, coarser hair, that's heavier and longer because of the difference in length and thickness from the finer hair of childhood the affect that is created both from wearing underwear and other clothing combined with gravity and the different texture causes the hair to curl although it's mostly the change in texture and clothes.