First of all, I suppose that how you define a "poor lawyer" depends on your definition of poor. As someone said below, many state employees (prosecutors, public defenders, public interest lawyers) may make below $40,000 depending on location. While that may be miniscule in comparison to some corporate big wig making 5 million a year, you have to recognize that even $40,000 is more than nearly everyone else in the world lives off. So, in reality, that is not really a realistic definition of poor.
If money is important to you, congrats ... you've chosen a good profession. Pretty much everyone I've met at law school is here to get a high paying job, and I suppose the idea of being rich is what enables them to get through each day of hell ... I mean, law school.
However, for me, my only motivating factor for staying in law school is the idea that I will one day be able to help others, and hopefully society by working in public interest law. While I may be making 1/4 or even 1/8 of what my fellow classmates will be pulling in each year, I definitely do not think I will be "poorer" for it. Many times, especially in law school, I think people forget the importance of non-material aspects of life and the quality they can add to your life. Alright, since I'm certain pretty much everyone that reads this is going to think I'm ridiculous, I'll stop here. But just to respond to your question again ... you probably don't see many poor lawyers because they don't go to law school to get a job that doesn't pay them big bucks. Ok, enough said.