My guess is that it harmonizes federal and state records for identifying individuals.
Or: How does one even begin looking into this kind of [non] arrangement?
(AFAIK, I'm not necessarily privy to the details of the dealings my state has with the federal government. I'd love to know where to look to see that kind of thing.)
In Ohio, you could show them a birth certificate and Social Security card and a few minutes later have a freshly printed ID.
If you got your hands on the blank ID cards and a standard commercial card printer, you could make fake IDs all day.