You know, I've asked myself this same question, Amy. Why do I care so much about homeless, abused, abandoned and killed animals, esp. dogs and cats? Why will I get up at the crack of dawn and trudge through rush-hour traffic (which I never do!) to muck out poop-filled cages and dogs when there is a shelter full of seized dogs from a mill? I get very passionate and on my soap box about pet shops, puppy mills, etc.... but I don't take the same action for other situations, those concerning humans. And there are plenty of those!
I sometimes feel guilty for not doing more for "worthier" causes, but then... it's not in me I guess, it's not what makes my blood boil and stirs me to action.
I have realized that we all need to feel passion for something, some cause, some greater good and I suppose there have to be people that are willing to do anything for all the causes out there, be it to 'save the caterpillars' or the beluga whales, the women of the Congo, the medicare system, the child workers in China, or teen pregnancy, etc......... I dunno, I agree with asking the question. I think it's important to ask it. But I also think that it just takes all kinds of people to make this world a better place. ...... and we've still got a long way to go.