It's not an ID
"The Social Security card was never meant to be used for identification purposes.
When the system was created in 1935, to assuage the concerns of American citizens, Congress insisted that the card would never and should never be used for purposes of identification.
Its sole purpose was to ensure that workers were paying the required payroll tax. Individual workers were assigned numbers so that the proper governing authority could easily account for the contributions made to the Social Security fund." 1
The fact remains that the Social Security card has no inherent value as an ID. There are no unique markings, photo, or identifying features to aid in identifying the bearer. There is only a name and a number.
1 Testimony of Michael Tanner, Director, Cato Institute, Project on Social Security Choice, before the Committee on Ways and Means - Subcommittee on Social Security, May 17, 2005