Undocumented immigrants are a useful scapegoat politically, because it allows those in power to point the finger at them for all the country's problems, but those immigrants have no political power themselves since they can't vote.
Additionally, it gives business owners a bunch of workers they can exploit, since those workers can't go to the police or report them to the labor board.
Additionally, it gives business owners a bunch of workers they can exploit, since those workers can't go to the police or report them to the labor board.