They're too busy. Don't ignore the social aspects of volunteerism. For many, the fringe benefits of volunteering include a chance to meet people. Many feel volunteering is better than singles bars, dating services, or personal ads. Some charities have established special singles' groups in order to attract volunteers.
Groups can work on projects, or run events to raise money for the charity.
Just beware of letting socialization get in the way of getting work done. A University of Michigan study found that people who spend even just an hour or less per week volunteering lived longer. This allows your group to use a mathematical formula to determine your annual lobbying limit as a percentage of your income. Lobbying is defined as activities intended to influence legislation, including communications with members, legislators or staff, government officials, or the general public. However, charities may not, under any circumstance, actively support or oppose a political candidate.