Providing amnesty just sends the message that if you break the law successfully enough, for long enough, that you will be rewarded with exactly what you broke the law for.
Every single day here they perpetuate the crime, every tax dollar they don't pay, every job they take, every identity they steal, every child they have are fruits of a rotten tree.
And the message that is sent is "yes crime is bad, but if you're sneaky enough, if you dupe the US government for long enough, not only will you not be punished but you'll be rewarded beyond anything you could possibly hope for in your home country."
It tells people living in their shit hole country thinking about breaking the law that yes, it is actually worth risking death and rape and torture because there is a pot of gold waiting for you if you pull it off and last a couple decades without getting caught.
The message we SHOULD SEND is that you will not succeed. Even if you go undetected for a while, you'll be unemployed, unable to drive, unable to get loans, unable to attend school, unable to do anything. If anyone employs you, not only will you be punished, but so will they. If your spouse tries to marry you knowing you're illegal to give you an out, they'll also be punished. Your children will be punished. Your country will be punished.
You WILL go home, and when you do your entire family will be humiliated, your country will be humiliated, you will not only have gotten nothing but you'll have wasted your time and lost your chance at any hope of legal migration. People will laugh at you, and then they will forget you because you are nothing here. You do not belong here. If you took advantage of any system while here you'll be fined on top of the deportation.
If you manage to stay sneaky for decades you will not be rewarded. You will be punished. The more ways you tried to go undetected - theft, identity fraud, sham marriages, going to the ER to avoid paying for routine care, under the table pay - the more ways you'll be punished. Fines, blacklisted from legal migration, and anyone who helped you do any of this knowing what you are? Also punished. Fuck off. There is no forgiveness here. There is no amnesty. Only punishment for criminals who disgrace the country with their illegitimate presence.