Good Question.
First, I'm not selling anything. Joining the LDS church is free. Getting a Bible or a Book of Mormon is free. While some people arent interested, there are thousands of people who are looking for a church, or have deep questions that we can help with. Few are sitting in their home thinking "the thing that would complete my soul would be a new home security system. I hope somebody knocks on my door and offers me one." It happens with Religion ALL the time.
Plus, there are some parts, even in my mission, which was pretty nice, that are really bad. South Sacramento and Stockton are rough areas. I was helping people turn their lives around, giving job training, and doing real community service as well. I feel pretty good about what I did out there