Male Baldness Info

An observation: Men with little hair on their heads, in general, have lots of hair on their faces, arms, chess (and I assume all over).
Why is that so? Is there any genetic/scientific reason?

is the onset age of male pattern balldnesss determined by genetics?
for example, every guy in my family hasnt started balding till their late 30s early 40 with no early balding or premature balding.
i am 18. does this mean that i dont have to worry about male pattern baldnesss until my late 30s