The card system isn't really airtight, as people said before; people will trade them or use them for others, whatever. It's not hyper-regulated (You can get by without ID in some cases, for example) and the regulation that does exist is easy enough to circumvent. That said, there's not all the much to regulate anyway.
The system doesn't really provide all that much and the rules, which are sometimes extensive, aren't legible to everyone, thus both incentivizing and also failing to regulate so-called "abuses" of the system (which are really people just disobeying the rules, nobody's balling offa food stamps). It "works" in the sense that it's better than nothing and still creates a cushion wherein families with unemployed earners can still manage to do important things like send their kids to school and whatnot. I know a few students who were surprised when they found out their families had been on food stamps or other welfare even while their parents had managed to send them to college.
So America's push to gut welfare system is really just based on the idea that rule-breaking in and of itself is bad. In reality, the rules aren't really doing all that much to benefit anyone anyway. Efforts to gut America's welfare system are absurd. Gut what?