If we had a USB or negative income tax system then that benefit would be clearly spread across the whole population evenly but instead the stamp system has many rules and restrictions that allow Walmart to strategically benefit by both positioning the role at just the right amount to qualify for the benefit (but no more) and frustratingly by being the vendor honouring the stamps.
But we do? The EITC is basically a negative income tax.
https://en.wikipedia.org/wiki/Earned_income_tax_credit
>I think the argument is that their labour is being subsidised which amounts to a benefit for BigSam.
Ironically negative income taxes are closer to a labor "subsidy", than food stamps, because they're contingent on income (ie. labor), unlike food stamps which don't give you more money if you make more.
Do those people magically start needing food and healthcare once they're employed by walmart? Why is it suddenly walmarts problem the moment they become a walmart employee? Would anyone stakeholder in this situation (the employees, society, walmart) be better off if the employee was no longer employed?