Because teens are the most problematic age. Also, there is the fast growth of long limbs. Large size and weight of the body and internal organs growth quickly.
Because adolescence is the age where a lot of problems. It is the fastest growing age with long limbs. Tall body Size and weight ratio of visceral rapid growth.
Because teenagers are young with many problems. It is also the age of the fast growing long limbs, body weight, proportion of gigantic size and internal organs grow quickly.