Families provide individuals with an important support system, not just during childhood but throughout life, and they provide society with a structure for passing along a culture's values from one generation to the next. Both of these roles are crucial for a culture to maintain consistency as decades and centuries go by.
One of the more tragic events in a child's life happens when parents fail to provide the structure of support. Many times, other family members are able to fill in the gaps and help raise the children, which still reinforces the family structure. However, in the most tragic cases, a governmental agency has to step in and take custody of the children so they do not go through the horrors of neglect. In situations like this, though, the family has failed the individual.
The role of the family in society is also significant, because the family is the transmitting unit of the values of a culture for the next generation. When children learn the right ways to behave and handle themselves at home, then they are more likely to contribute effectively to society and have a content, productive life. Families that do not transmit those values do a disservice to society.