It stems from a conflict of need and want from what I understand.

The need for a national id and the refusal of the citizens for a national id. There was a lot of controversy about the SSN because it could be used as an id and the people didn’t want that being so privacy conscious, so they made the numbering system simple and that card fragile to show and dissuade that it isn’t a good id to get the SS passed.

But of course, there’s still a want/need for some kind of unified id across the nation - so it was used anyway

And thus we have a terrible id system: flimsy, deterministic, and mostly-unchangable

If you know the social security number of someone born in your hospital in the same day, it’s likely your ssn’s are right next to each other and could be guessed

At this point, I don’t think there would be much resistance to a national id, and it would be great for an update that is both securely random, and changeable so that leaking your SSN isn’t such a crazy risk, having it in a laminated card with a chip and electronic signature even better.