up till late 1990s SSN and DOB were public information, as they were printed on never-secured student IDs in American schools, for instance, and who knows where those unprotected lists went.
my email address at the university from 2000-2003 had the last 4 of my SSN in it.
I had orders in the military listing hundreds of people’s name and SSN. This was ~2007
This practice went on all the way into the mid-2000s at least (I graduated in 2006 and my SSN (which doubled as a student id) was printed on my student ID back then)
My university used it as the student id, so who knows how many hundreds of places that got copied. Including smeared all over the virtual desktop systems as it was your login identifier.