Why is is that hair on your head keeps growing?

Question

While the hair on other parts of your body, i.e. legs, underarms, eyebrows, etc. grows to a certain length and then stops.

Answer 1

hair on your head does not keep growing, it just grows to a longer length than most other hair on your body. It varies between people, some people it stops partways down their back, others to their butts. You'd have a tough time finding someone with hair much longer than that, no matter how long ago their last haircut was.