Sure, but it also prevents poor people without access to a kitchen from having hot food.

Do we even know that people reselling hot food would be more of a problem than people reselling cold food? Wouldn't it just be easier to review the transaction data and detect patterns of actual fraud? Is the cost of doing any of this actually lower than the cost of fraud?

Exactly. Poor people are then forced to burn stuff to make heat, which often releases carbon dioxide, unlike clean burning methods using magnetrons.

Forced to? No.