All an illegal has to do is file exempt on withholding and FICA and they'll take home more per hour than a legal worker. If they remember to change their fake ID between Thanksgiving and New Years then there's hardly a chance of them getting caught.
Add in welfare scamming for icing on their cake.
No FICA, no minimum wage, no overtime, no medicare, no unemployment insurance, no workmans comp, no employees whining to the EEOC/OSHA/etc, no tax penalties for not offering an employer health plan...
It’s all good, and as the govt regulation and tax burden grows it gets even better!