Everyone has heard stories of abuse in the food stamp / EBT program over the decades of its existence. These stories detract from the purpose of the program and these abusers are literally taking food out of the mouths of hungry Americans.
The food stamp program was created back in the day when prices for each item were typed into a cash register. Today's modern Point of Sale system handles this via a scanner and computer look up of the UPC code.
It is very easy for these modern point of sale systems to categorize food categories - something that would have been too much to ask of the human cashier in the old days.
Simply put reasonable bounds in place to prevent purchases of expensive items like $10+/lb steak and seafood. Taxpayers don't want to fund such luxuries.