[jjmarr]

Until 1986[1] most Americans didn't get a Social Security Number until their first job.

In The Matrix (1999) there's a scene where Agent Smith explicitly remarks that Neo has an SSN as proof he's a law-abiding citizen in a white-collar job.

[1] when it was made a requirement to claim tax deductions for dependent children. Even today, if you don't want the tax break, you can opt out at the cost of ruining your child's life!

[sejje]

I was born before that and issued my SSN at birth.

[jjmarr]

The first pilot project to issue SSNs with the birth certificate automatically was in 1987. You can read the history here:

https://www.ssa.gov/policy/docs/ssb/v56n1/v56n1p83.pdf

Prior to that, getting the SSN required giving your birth certificate to the government. If the family wasn't getting government benefits, many didn't bother.