All over. We have tiny hairs all over our body! Our face has soft small hairs, our arms, legs, trunk etc. And obviously on our heads. After puberty we have more noticeable hair in the armpits and groin. Some women notice upper lip hair that is annoying. Electrolysis can help cosmetically. Hair has a function...It will stand up in fear to alert us and also before a lightening strike. Hope that helps.
Nature/culture. Most of the body surface has hair in some form but the decision on where to let it remain is more cultural. People have been shaving or plucking hair on selective body surfaces since as early an ancient Egypt. Times change and cultural expectations will also. Why some women choose to remain hairless in some ares and not others is under these influences. I see no right or wrong, just personal choice.