 People conform and change their behaviors in order to fit in and go along with whatever their friends or whoever they think their friends are at the time. Because any deviations from what is accepted at large causes shame most of the time. And most deviations from the social norms are treated with a negative response like guilt and shame. So most times you'll never ever see a person's true side, even if you've known them for a very long time. Because they're afraid of being judged and shamed for who they really are. But no one's watching them.