Adolescence is the onset of adulthood before the capacity to function as a real adult in the real world is reached. One of the things that adolescents search for is some form of personal validation besides their parents and immediate family. It is probably close enough to true that we are biologically driven to look for this outside acceptance.
Unfortunately our society favors heavily segregating children based on age. That results in confused & clueless teens begging for acceptance from equally clueless people from the same wing of the same asylum.
Once in the real world a functional adult who can hold down a job finds there are a million ways to find personal validation. Teens do not have that opportunity; they (often) imagine that the opinion of other teenagers is the only path to validation.