So what happens to those who fail the drug testing and are denied public assistance? They don't get to pay their rent, utilities, or buy food and other essential supplies(iphones) for their children. You then put more people on the street, who often end up becoming recycled within the criminal justice system. Now with a criminal background and no essential technical skills, you end up having someone dangerous walking around on the streets.
Those of us with jobs are held to higher standards than those who do not, so often we must subject ourselves to things like drug testing, psych evals, polygraphs, interviewing, and other standard testing.