Answer the question. How uninformed are you? Do you think employers are able to pay wages under the table without immediately triggering reporting mechanisms that tell the government? You think one construction company can pay zero payroll taxes, while their competitors are paying payroll taxes for tens or hundreds of workers, and no one would notice?
Anyways, this would be a worthwhile read for you:
https://bipartisanpolicy.org/blog/how-do-undocumented-immigrants-pay-federal-taxes-an-explainer/
I know an owner of a Piggly Wiggly (massive grocery chain) who also owns a couple other businessess.
One of his staff who is illegal works under a fake name, he punches a clock and gets a regular paycheck. Of course taxes are taken from that check.
This owner, a middle aged Italian from the midwest actually learned Spanish so it would be easier for him to find this kind of labor. He actively sought to employ illegals.
Here is where it gets interesting.
We will call this employee "Pete". That's not his real name, but anyways, Pete is a nice enough guy, I knew him for a few years.
Pete also stays after his shift ends in his department and does maintenance off the clock for the owner. He punches out at his scheduled time, and works an additional 20-30 hours a week. I've seen it firsthand, and I've talked to the owner and Pete about it. For this extra 80-100 hours a month, the owner gives Pete an extra $100 a month in cash. No, I'm not kidding. About $1/hour.
So what does Pete do for those extra hours? A few things, store maintenance, cleaning and minor repairs. Now if he didn't do that, the owner would have to hire another employee (or 2) for the maintenance department. He also would do maintenance on our delivery vehicles, plumbing repairs, work on our HVAC system, and he specialized in eletrical repairs. So if any fixtures or store equipment were malfunctioning, he would take the equipment to the loading dock and attempt to repair it, or stay after the store closed and attempt to repair whatever it was.
Wasn't a problem for him because he was an electrician in Mexico and he liked the extra cash to add to what he would send home to his wife and kids in Mexico.
Let's just say that one of the three-ish repairs that Pete made in a month would have required a call to a licensed refrigeration/HVAC/plumbing/electrical specialist. That's a whole lot money and work kept out of the hands of honest tradesmen.
Whether you like it or not, businesses large and small, left and right find ways to pay illegals under the table. It saves them lots of money, supressess wages and takes jobs from everyone else.
Feel free to tell me I'm making this up or ignore/minimize this post altogether.