It's trying to be a non-repudiation system based on something only you and they know. Unfortunately, without a credit history or paying utility bills, credit s

It's trying to be a non-repudiation system based on something only you and they know. Unfortunately, without a credit history or paying utility bills, credit sources alone aren't enough. So why not use other facts such as partial DoB, partial SSN, parent/s SSN, etc. only when no other details are available? It's not ideal, but it's better than either losing business or falling back on something much less secure eg facts that are in the public record.