Why is that? Bankruptcy is the alternative to debtors' prison. It recognizes, literally, the "bankruptcy" of the policies and practices of those declaring bankruptcy. It transfers the burden of any losses to those who had a vested interest in providing oversight but whose judgements were flawed.
The result of a bankruptcy would be that future lenders would hesitate to allow their assets to be risked using the same flawed policies.
As for Social Security, what mechanism are you suggesting that will prevent its bankruptcy? The bills cannot be paid, will not be paid, and the only uncertainty is when the Ponzi scheme will be allowed to fail. That day is fast approaching.
I fully expect, if I live another twenty years, for the unworkable "promise" of Social Security to be well and truly broken. It wasn't a good idea then, it's not a good idea now, and it will still be a bad idea on the day it fails.
It took seventy years for the Soviet Union to fail. Our approach to socialism might take slightly longer.
It took that long for the USSR to fail because of the USA propping it up at various times, via “lend-lease” and other programs.