Well, here's the deal:
A lot of people DIDN'T plan for retirement. That said, you are correct in pointing out that Social Security is a ponzi scheme and that communism (which Social Security IS) doesn't work.
When China dissolved it's 'Iron Rice Bowl' program completely (equivalent to social welfare for 'retirement'), the result was that workers suddenly started saving like crazy for their retirement. Money velocity is almost nil in China right now because of it. There goes THAT economy! Worse, their government is STILL trying to 'build' it's way to prosperity by constructing whole cities that no one lives in, building facilities that less and less workers are using, and trying anything and everything to get people to spend money they don't want to spend because they are saving for their retirement.
China is in a real mess right now.
If Social Security were to be dissolved suddenly and completely, the same thing would happen here. We are ALREADY in an economic depression right now (started by DEMOCRATS in 2019), and killing money velocity like this would be devastating. Worse, it would probably result in a general revolt.
So...the 'federal' government is stuck. They can't afford it, yet they can't kill it either. Unfortunately, the only way for Social Security to end if an uncontrolled contraction of government, soon to occur since they are flat broke already. EVERYTHING the government does is now running on tick, either borrowing or printing the money out of nothing to do it.
...and the crows are coming home to roost... Dollars are returning to the States from abroad. Nations are dumping dollars and conducting international trade with less and less of them.