You are right that SSNs have been required for years...for citizens.
The IRS has been issuing different numbers to illegals so they can use them to qualify without SSNs for them or their children. Illegals have even been able to claim children living in Mexico- that may not even exist.
In many cases illegals have used other people’s SSNs to file for tax credits as well. The IRS has been choosing to ignore Social Security when they tell them a number does not match.
And nobody cares?