Why does the hair on the sides of the head not fall out like the hair on the top of heads?

Why do men lose the hair on the top of their heads but not the sides? I'm not asking why men lose their hair due to male pattern baldness/genetics. I'm asking why the hair loss only happens on the top but not the sides of the head. Ex: http://www.greysanatomyinsider.com/wp-co

Notice the hair loss ONLY on the top of the head. What is it about the follicles on the side that cause them to retain hair while the follicles on the top cannot retain hair?Why does the hair on the sides of the head not fall out like the hair on the top of heads?
Pretty good question: the basic 2-cent answer is ';no one knows';, but what we do know is that for most men the hair on the sides and back do not have the genetic sensitivity to DHT (dihydrotestosterone) degradation of the follicles like the hair at the hairline and crown does. Body hair also seems immune as well. The problem is no one knows why these specific hair follicles are genetically immune.

Indeed this isn't the case for all men- some men do get loss on sides and back due to DHT sensitivity- and a few others also have autoimmune reactions to their own hair- either of these causing hair loss over the whole head and the latter often affecting the whole body while the former being a damn good reason to have the follicles tested before considering a hair transplant so as to ensure that both your money and your hair grafts won't soon miniaturize.

benefit cosmetics