Why does Harburg feel that "Brother, Can You Spare a Dime?" is a legitimate question, not just a plea from a beggar?

Harburg feel that "Brother, Can You Spare a Dime?" is a legitimate question, not just a plea from a beggar because he wanted to make people think that the system stole the job of a beggar. Why the beggar is left to the streets, when the job is done and after all the hard work he had done. He wanted people to realize that beggars are also important to the society during the Great Depression.