why isnt there ever punishment for the businesses hiring illegal migrants and why are random low skill employers like restaurants allowed to get away with legally hiring foreign labor when there are people able and willing to fill those vacancies?

How is there NOT an incentive for employers to game the system by publishint job listings for random positions with inflated requirements and undervalued compensation so nobody who could otherwise do the job at the price listed and be hired domestically wouldnt or couldnt apply and they simply wail that nobody wants to work