You really think poor people living on welfare have that much of a choice? That they can jump to a different life the second they decide to?
Back in the years of slavery, people had the choice to escape. They weren't really kept in chains all the time; so if you waited for the right opportunity, you could run away. But then what? Even if you could avoid capture, where would you go? Who would help you? Who would trust you? Who would hire you? Who would mentor you in your new life?
You see? Fear is stronger than chains. Slave owners knew it, and today's progressives know it too.