However, social security and other government funded pensions are Ponzi schemes. The money you pay in is given to people who are retired at that time. The money you get out is paid by people who are working at that time.
So the real fight is what proportion of current output goes to old people. Private schemes try to ensure wealthy old people get the biggest slice. Public schemes are more vote driven. It doesn't make them Ponzi schemes.
It's also not just a pension fund as you can receive benefits well before 62. Death of spouse with under age children or permanent disability.
Now, this does not mean it's a great or even a good investment. But, the trade off of safety vs returns is not actually that bad assuming you live longer than average.
PS: Another way of looking at it is there are no 100% safe approaches to investing 10's of trillions of dollars. Your stuck leveraging GDP growth which is only slightly better than inflation and frankly that's what SS does.
Most pensions also will not be enough to cover long term care costs if you are unlucky enough to get some form of dementia.
Pensions as a concept were a great idea when life expectancy was shorter and most people could mostly look after themselves in old age.
I don't think they can survive large numbers of people living until 90 -100 with dementia and needing 24h care. Lets hope the Ai/robotics gamble pays out.
Consider if you have a 5% chance to die at or before 65 who get's the money? Well what if you could get together with 10,000 people and split it with those who live. Now your investments are boosted by those who die and there is no downside as who cares what happens after you die.
Unfortunately, such schemes are illegal unless it's though a company. Because really the long tail is living to 120 which means you don't want to aim to be broke at say 95 then turn 95 and be in good health.
PS: Remember, returns after inflation can be <3% over 20 years. I want a hedge for that risk other than just having a massive amount of money I can't really spend.