JG trades off with Medicaid and food stamps---people would be ineligible and have other means

That's because if we got a national job guarantee up and running, something else would happen too: Medicaid, food stamps, and other programs designed to help people in poverty would massively shrink. They all operate by providing benefits to people who fall below a certain income threshold. And with a job guarantee in place, far fewer people would ever drop that low (and in the case of Medicaid, they'd get their health care through their job, too). Spending on other social ills tied up with unemployment, from health problems to crime to incarceration, would shrink as well.