Having a job is not the only source of purpose there is. Handing out money may not be an incentive to work harder, but it can let those people look for different ways of achieving satisfaction other than just getting high.

People with no money tend to think they need to use any money they get ASAP on fast rewards, only when they have enough money to save do they start thinking about saving any at all. Of course this will hardly work to get those already addicted to change their ways overnight, but some long term financial stability can change the worldview of new generations so they plan for their own future instead of living like they were to die tomorrow.