In your case, it was possible because of the two conditions given below. Thats not true in our case.
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At one point, anyone on visas other than business/visitor could file for SSN or a Tax ID. That's no longer possible unless: 1) You are in the US on a legitimate Visa that allows you to work & 2) You have an offer letter for paid employment.
Now students on F1 visa (who are allowed to work part time on campus) can't get SSN unless they pick up a job and have a letter to prove it. Earlier they could.