Usually social norms are created by having uniformities in certain behaviors of the social group members. Also, there are usually negative consequences when someone violates a social norm. Norms do serve a purpose, as they allow people to expect the events that will occur in a particular setting. This allows people to prepare themselves for being in that situation.
Uncertainty is a big source of psychological stress.
Norms allow us to reduce the uncertainty that we might otherwise feel in a situation, or leading up to a situation. However, norms can be self-perpetuating, as once they are established they will often continue, even when those who established them have long since left the situation. For example, medical physician training, and other rites of passage. Authority derives from the status not any particular person. Obedience behavior change produced by the commands of authority.