Hair depends on the follicles it grows from for it's cellular . Straight hair grows from round follicles, curly hair from kidney shaped follicles. It is through these follicles that hair get's it "information", colour, texture and terminal length. Different follicles will cease to add more cells of keratin( Hair substance) at a pre-determined length and ALWAYS will, After that period of not growing, they generally shed and a new hair develops. This is why pubic hair never passes the knees etc!. It also accounts for the difference in texture to the other body hair we have, which we are all covered in to differing degrees, the term is LAGUNOUS hair which develops when we are in the womb, when lagunous follicles are "charged" with sex hormones, Testosterone for men and Oestrogen for women, the hair develops in characteristic areas for the sexes. (Women who do not remove their body hair often display similar growth patterns on their bodies as do men-pits, stomach, small of back, nipples etc- like it or not, it's nature!)
The purpose of body hair is interesting to note, not only does it insulate our bodies- and I don't mean a fur rug effect, but the reason each hair has a muscle controlling it's position is to trap a layer of air close to the skin which can insulate the body from coldness. It is thought that it also serves as a sunscreen deflecting the rays of the sun shielding skin from direct burn and even increases sensitivity making the person more aware of contact or environment alerting the person to danger or tactile sensation.
Hair colour changes over the years as it does from area to area. My head hair is dark, my eyelashes and beard black leg hair is brown-blonde. My pubes are certainly not curly and neither is my underarm hair, which I'd describe more as coarse textured straight.