Some places (colleges were very bad about this) would use your SSN as both an ID and a password - so to buy at the cafeteria you’d swipe your student ID and your PIN was the last four of your social.
Some workplaces did it too. It’s mostly gone now, but pieces still remain.
Given that many college students don’t even have SSNs (international students have no reason to get one until they want to work somewhere), this makes zero sense. What college does this?