There are social norms that establish how we should behave and present ourselves in specific situations. These standards establish which clothes are appropriate for the home situation. According to social norms a wedding is a formal event and requires people to wear formal attire at this event. Jeans and T-shirts are casual clothes and are not appropriate for a wedding. For this reason, we can say that when David's parents say that he needs to wear a suit to go to the wedding, they are teaching him these norms.
