You could work at National Geographic and bring the realities of living in developing countries to the forefront of our minds, motivating thousands of readers to donate or become involved in relief efforts. Or you could just do a really good job on little Trevor's first acting headshots. He might even book a commercial with a picture of himself so artistically captured.
Basically, there won't be much glory to this job, unless you really sacrifice your time, energy, and well-being to get it. The photographer who creeps behind enemy lines or infiltrates secret government meetings might spark real change with his or her photos, but it's tough to say the risk will be worth the reward. That'll be for you to decide, shutterbug.