A childhood belief about getting older

My parents grew up in the Third World nation and my mother and my father's height was only 5' 2". I used to think that if my parents would apply for a job, watch R movies, purchase alcohol, drive, or anything that is for grown-ups, people would might say that they're still a child or they're not adults yet. Because most of the people that I see in America were at an average stature from 5'7 to 5'11. In my view, my parents were like teenagers because of their height.