Increasingly, social norms are being used to encourage pro-social behavior. They have been successfully used to encourage:

• Healthy eating
• Increase attendance at doctor appointments
• To reduce tax evasion
• To increase towel reuse at hotels

People tend to conform to behaviors that are common among other people, even when they know that those people did not make their choices freely, and when the decision does not mirror their own desires. 

The idea of the self-categorization theory is that people conform to the norms of certain social groups whenever they have a personal desire to feel like they belong.

It is irrelevant whether a norm reflects people's preference, as long as the behavior is associated with the group.

• One common explanation: we that if everyone else is choosing to do one thing, it is probably a good thing to do.
• Another common explanation: we fear that failing to follow a norm may have negative social consequences.