Ooops that's a felony...
It's also a redundancy, given that your SSN is part of the registration info in the database. They know where you most likely can be found.
It's a small Cold War relic that will never be used again for it's intended purpose with enormous power to prosecute.
Until Obama, weaponizing the IRS was a conspiracy theory.
President Kamala Harris puts her cronies into the Selective Service System and has them pulling who and who has not been updating their data for possible felony prosecutions?
Get rid of the damn thing.