They're in it for the prestige. Showing people that you care about the homeless is a sign of moral virtue, regardless of whether you're actually trying to help.

Consider what the jealous groupies sing about Captain Hammer's girlfriend in Dr. Horrible's Singalong Blog:

    So they say he saved her life
    They say she works with the homeless, and doesn't eat meat
    We have a problem with her!

Why equate working with the homeless with not eating meat? Those are both displays of feminine caring.