A social security number/card is not exclusive to citizens. Green card/permanent residents, for example, usually get them - particularly, if planning to/already working.
Any kind of national/citizen id would need a whole new process and require it be provided to 100% of existing citizens. Time-consuming and certainly a cost associated with the process.
It's one of those "in theory" easy things, but a lot more difficult in practice, I imagine.
A social security number/card is not exclusive to citizens. Green card/permanent residents, for example, usually get them - particularly, if planning to/already working.
Any kind of national/citizen id would need a whole new process and require it be provided to 100% of existing citizens. Time-consuming and certainly a cost associated with the process.
It's one of those "in theory" easy things, but a lot more difficult in practice, I imagine.