It is a very fair question. Many "philanthropists" make a living from their work, sometimes a very good living. It also looks good on a resume or c.v., can be used indirectly to build wealth. Most commonly, I think, those of us who do volunteer work with people considered vulnerable due to poverty or trauma or what have you are trying to look better to ourselves and others. Teju Cole calls this "The White Savior Industrial Complex." Helping Africans is about "having a big emotional experience that validates privilege." Being a person born into privilege with more than a little bit of ambition and insecurity, I must admit that a desire to build myself up has had more than a little to do with my volunteer work with battered women, vulnerable children, racial reconciliation, and Kenya and Ghana.
But I also learned slowly, over the years, that the biggest pay-off in all of these activities was the relationships that they brought. It may seem odd, but the happiest people I know are those who see their lives as a vessel to be joyfully emptied on behalf of others. With Yo Ghana! I get to work with dozens of such people: the best of the best teachers, people who already have too much to do yet take on more; the principals and headmasters and headmistresses who face incredible problems with good humor and boundless energy; volunteers and advisers who are already stretched thin but sacrifice to support us with gifts of time and money. And people who are vulnerable economically are often very rich and generous in other respects. The month I spend in Ghana every year is a month suffused with warmth and inspiration I have found nowhere else. Our slogan, "exchanges for transformation," certainly applies for and to me.
Religion tell us that service is good for the soul. Evolution tell us that we are hard-wired to care for each other, that our survival has always been a collective endeavor. And experience tells me that happiness comes from finding people doing great things and joining them.