Human beings are acutely responsive to how other people perceive, evaluate and feel about them.
As humans we all yearn for acceptance. In our hunter–gatherer past, humans lived in tribes; our safety depended on us being accepted and remaining within our tribes. Any sign that we would be thrown out of our tribe resulted in acute anxiety and a desire to conform.
In our past, this was akin to the death sentence.
We would not have survived alone, and often in our hunter–gatherer past, this would have resulted in us feeling ostracised and unworthy of existence.