Parents and children get to know each other with new perspectives and on different terms than they ordinarily see each other. Volunteering as a family can also change your family dynamics - try putting a teen in charge of a task from start to finish with no parental controls in place. Afterwards, however, I still wonder why they can't clean their room when I ask sometimes. Families share a common experience that they will talk about for years to come. Kids see their parents in a work setting.
Parents help foster a work ethic in their children.
Kids and parents both learn new skills - like building a deck or repairing a door. While working together, there is time to share ideas on value and ethics in a setting quite different from home. Families that work together learn about themselves. It's not always the parent that comes up with the solutions. Parents and children exchange ideas when confronted with a problem.