The reason SSN became a form of ID in the first place was because it's the only way to track a person across all states. If I get a loan in California, then mov

The reason SSN became a form of ID in the first place was because it's the only way to track a person across all states. If I get a loan in California, then move to Arizona and apply for another loan from another bank, the new bank should still be able to know about my loan in California. SSN was just too convenient for that purpose and banks stuck with it even though it wasn't designed for it.