Portraits were originally for the rich and powerful to show off how rich and powerful they were, however when the camera was invented it made it easier to have your portrait taken, so it was affordable for less rich people to have thier portrait taken.
Diane Arbus was a photographer who focused on black and white portraits of exposed people, she focused on exposing people as being worse than the actually are. in 1972 Diane Arbus comitted suicide from dipression she had been suffering for some time before her suicide.
Larry Clark's took photo portraits about his own life, instead of most other portraitures who delve into other peoples lives and take pictures of them. Larry's photos were mainly about sex, drugs and violence, very controversal for a portraiture, because portraits usually consist of people with clothes on. Larry's ken park was banned for its graphic content of drugs and nudity.
context
Portraits were originally used for the rich and famous who could afford it at the time, consisting of the persons head as the main part of the picture. When cameras were invented it became easier for people to have their portraits taken,