From what my wife tells me (the retired HR director) it is Federal LAW that any and all new hires MUST prove they are a citizen, and show the physical Social Security card. Since you are new to the new company they are required to start over with new everything.
It is just the feds doing the "paperwork reduction" and simplification bit.
The really stupid (only our federal government level of stupid) is you can't ask if someone is an illegal immigrant. If they hand in poorly forged documents you are supposed to accept them. Otherwise it might discriminate against illegals.
