It's not natural. It's a social construct.

If you really want to understand the truth about teens, it's necessary to acknowledge that 'adolescence' is not a natural state. It's something modern society made up. We raised the age of social adulthood creating a gap between it and biological adulthood. That dissonance creates our well-known behavioral issues at that age. Cultures that don't infantilize their young adults don't get those problems.

see: Margaret Meade or Schlegel & Barry.