They didn’t “pay into” anything. Payroll taxes are just taxes. There is no lockbox, trust account or anything else. The money is simply spent as it comes in - just like the money from income taxes, tariffs, etc. I am no more entitled to something because I have paid payroll tax all my life than I am entitled to something because I have paid sales taxes or income taxes. The idea that paying payroll taxes is somehow “special” is just another government engendered delusion. Social security is just another income transfre program - welfare without much of a means test.
SS is full of IOUs.
Do you understand what that means? It means there is a huge surplus that was borrowed for other purposes.
Think about that.