But I would point out that people CAN (and do) scam the system.
Here's how the scam works. You get a EBT card. You're right, you can't just get the cash off the card.
So shady retailers offer a service. You walk in with $100 on the card. You give them the $100 card, they make $100 in government cheese presumably for the WIC approved food items they sold you. But instead of groceries they give you $50-75 in cash.
There are harsh penalties for trading SNAP benefits, but this sort of isn't unheard of. Do a quick search.
That said, all things added up supposedly fraud only accounts for 1% of the nearly 80 billion dollar program. 1% of a huge number is still a large amount.