In Jim Stengel's Grow, Eric Ryan, founder of Method, describes why companies should be purpose and cause driven:

When you articulate an ideal and create a cause, it gives people, including myself, the ability to do so much more. You're so much more excited to jump out of bed and go to work when you're doing something that improves people's lives. It's just so much more enjoyable and you produce so much more, because you're part of something bigger.