I agree that this is frustrating.
If a citizen engages in ID theft, they are punished when caught. An illegal alien does it, it is written off. If you're an American who had your ID stolen by one, the IRS won't even help you.
They work under the table in mass, and their children use public healthcare and schools the parents and the children on average will never pay enough in taxes to pay back. So they use more services than average AND are guilty of income tax evasion in most cases. Those working under fake SSN numbers are only committing fraud, while those using someone else's SSN are doing identity theft and tax fraud.
I'd forgive it more if I could ignore tax law when they ignore both tax law and immigration law. But if I did a fraction of that, I'd be in jail.
The illegal aliens and even many legal Mexican immigrants who have wracked up multiple DUIs get off on allegations of ignorance, even after they've killed people in drunk driving accidents. An American has repeated such offenses, they lose their driver's license for life.
If someone has proven they already don't give a flip about immigration laws, they are much more likely to ignore all the others, too. Then you get the illegal immigrants who commit crimes, get deported, come back, and because they aren't arrested for their repeated illegal acts, they commit more crimes than many people who are citizens.
Why aren't they prosecuted? Because big business that funds both parties like the cheap labor that is pliant because of its illegal status. And Democrats support it because these are potential future Democrat voters. After all, if they were going to vote Republican, you know Democrats would slam the border shut.