The SSN they apply under comes back with diddley squat for income (likely a kid's), and any income is cash and never claimed.
Unlike some segments of the population, many of those from South of the Border are good and able workers, and have no qualms about gaming the system.
Got mixed feelings about that, at least they WILL work, and honestly enough at the job that they are kept around.
But it’s like they feel they are the deserved instant karma to America’s foolishness, too.