They were invented only for the Social Security system, which is the American version of a public pension system, but get used far beyond their original mandate.
I don't know how banks are with doing checks now, but one once issued a credit card to my dog after a drunk party guest applied on his behalf with a randomly-generated number. (That was a weird call to a fraud line...)
A silly instance of Mastodon for queer folk and non-queer folk alike. Let's be friends!