Jung’s conception of introversion and extroversion comes from Freud, and had less to do with liking to be around people and more about your cognitive functions. Jung expanded on Freud and began to articulate a personality typology. Modern MBTI tests will pay lip service to Jung when results don’t line up with self-perception, though the content is quite far removed from Jung aside from the fascism and the spirituality. In the United States, at least, these tests are in practice somewhat deterministic because we have many superstitious idiots in powerful places.
The original Myers and Briggs were a mother and daughter team, which started with Myers, the mother, doing psychological experiments on the daughter, Briggs, during childhood. Myers was obsessed with Jung to the point of writing self insert yaoi fanfiction which was rejected by every publisher she submitted it to. In the decades following WWII, the CIA was conducting a lot of personality research (think: Black Panthers, Weather Underground, Courtney Love), so Briggs was finally able to find institutional backing. The findings suggested personality resisted type and that theirs was a fraught taxonomy, so they were ultimately booted from the lab. The daughter was still able to sell the exam to Human Resources departments who, being populated by middle-class white women in the 70s, were a bunch of self-help heads and wanted a way to weed out rebels and slackers. From the outset, these types were codified to mark people as unemployable. Both Myers and Briggs believed everybody had a potential and some were best relegated to menial existences in the home. I read a biography about them because I wanted to prove to a friend it was bullshit.
Yes I did get ENTP and no I do not have a full time job.