Author Gretchen Weber makes the case that a socially responsible company can attract talent that is interested in more than just a wage.
"Researchers at Stanford University and the University of California, Santa Barbara, surveyed 800 MBA students from 11 leading North American and European business schools and found that 94 percent would accept a lower salary--an average of 14 percent lower--to work for a firm with a reputation for being environmentally friendly, caring about employees and caring about outside stakeholders such as the community."
- from her book, "The Recruiting Payoff of Social Responsibility"
Seems to me that it's just a part of your reputation, which always plays a role.