There are guys who are illegal who have an unwritten rule:
Do not break the law, even a misdemeanor, pay your taxes, do not attempt to claim social benefits, keep your head down and do your work and do it well.
They hope that one day they will get the opportunity to get the green card and become documented.
From Vox in 2018:
The most recent IRS data, from 2015, shows that the agency received 4.4 million income tax returns from workers who don’t have Social Security numbers, which includes a large number of undocumented immigrants. That year, they paid $23.6 billion in income taxes. That doesn’t even include workers who paid taxes with fake Social Security numbers on their W-2 forms, which is also common.