Because the MONEY is Federal money. Part of the paradigm which creates ‘pork’ is the notion that each state representative is somehow expected to ‘bring home the Federal bacon’; in other words, I’m a good representative for Massachusetts if I can get more money out of the Federal kitty than Massachusetts contributed. So the incentive is always to spend more because its not ‘our money’.
If a state funds their own food stamp program, I could care less how they spend the money (unless I reside in that state).
And because they couldn’t find a job to earn any money to put any food on the table.