In Antiquity, Family and Community Provided a Safety Net in Retirement
Throughout most of human history, the idea of retirement as we know it today didn't exist. People simply worked their entire lives either hunting and gather or farming (after the Agricultural Revolution) -- if they were lucky enough to survive into adulthood -- and when they were too old to work, they relied on their families to take care of them. An old person might rely on younger siblings, children, and nieces and nephews within the family or community to take care of them. While doing this they probably still had to do some work - the idea of not working at all is a deeply modern notion and even very old people in ancient times still likely cared for children, did chores around the house, and performed other familial duties (eg. arranging marriages, representing the family to other communities, and advising younger family members).
Although life was incredibly harsh with humans having to face both natural disasters and man-made dangers in the form of banditry, war, pillaging, or abandonment, most human societies operated in a way where the elders and those who were unable to work were taken care of by family. As time moved forward and as humans settle down this was more and more true - while a hunter-gatherer tribe might leave an old person to die, a farming community would likely be able to provide for the elderly because life was calmer and a bit more stable in terms of movement and physical danger.
Obviously, no one in their right mind living in the first-world should want to go back to a hunting and gathering lifestyle and especially a farming lifestyle (as farming was likely worse than hunting and gathering for overall human well-being). However, we can't deny that the family bonds that existed in the past that effectively created an organic safety net for the elderly no longer exists today.
Safety Nets Such as Welfare Provide Retirement Security in a Changed World
As the world moved forward modernized, nations around the world began creating public, centralized welfare systems to take care of those who were too old to work and had to enter a stage of retirement or diminished income-earning capability. In the United States, during Roosevelt's New Deal during the Great Depression, the Social Security system was created - this was a system where old people who were no longer working could receive income from the government (meaning from those who were earning income). In effect, this wealth-transfer mechanism sought to replace the old traditional familial and community retirement safety nets that had long since been eroded over the centuries following the Industrial Revolution.
It is difficult to argue that a safety net for old people who can no longer produce income through their labor and who don't have a large enough retirement nest egg to live on is a prudent idea - it is deeply natural to humanity to take care of one another. The difference is that instead of taking care of each other locally, we started taking care of each other on a grand national scale. This creates its own problems and perverse incentives, but it fundamentally is in line with our human nature. If done in a prudent and conservative way (something that is far from guaranteed), such a retirement safety net can at once benefit the economy through stabilizing things and benefit society through creating a better and healthier moral landscape by taking care of retirees.
Retirement Saftey Nets in Jeopardy - Self-reliance is Key
However, today the Social Security system -- a system that hasn't even been around for a century -- seems to be in jeopardy (it is projected that in 2037 Social Security trust fund reserves will be exhausted and where 100% of payments will no longer be able to be made). A system designed at a time where there were few retirees living into their 60s and 70s compared to the working population is under stress in the world where Baby Boomers are aging rapidly with access to world-class health care that will allow them to live into their 80s and 90s reliably and in good numbers. Many believe this system will not be able to sustain itself. This will be further exacerbated if unemployment increases over the coming decades due tot he rise of artificial intelligence. Young people today should not rely on Social Security to be around when they are old and gray - that is now a foolish proposition.
For young people today, the idea of retirement is different than for almost all past generations. For the first time in history, neither (1) the familial/community structure that effectively provided retirement benefits for the old nor (2) the retirement benefits provided by welfare systems like Social Security is likely to be around when today's young men and women reach retirement age.
So, we're now in a world where the old family and community structure have long since been almost totally wiped out and where the retirement safety net that came in to replace that old structure is itself in peril. We are facing a troubling and dark world when it comes to retirement - we have neither one nor the other, we only have ourselves at this point. Although a fix might occur and things might turn out well, in the end, any prudent person who is under the age of 40 should discount Social Security and only rely on himself/herself to provide in old age and retirement. This requires changes - it requires a discipline that might not have existed in the last century for most of the population in term of saving. Young people must be diligent and disciplined savers and investors if they are going to be able to amass a nest egg large enough to support them through what could be decades of retirement.
This means that saving 5% or 6% in your 401k to get your employer match, putting $5000 a year into an Investment Retirement Account (IRA), or simply having a nice cash cushion in the bank is not even close to enough. Saving rates must far exceed 10% and should approach 25% if young people today are going to be able to comfortably retire. Additionally, effort and energy must be put in to invest the savings in a smart way - saving cash will not be sufficient as growth is going to be needed over time in order to build up a nest egg.