"The program's payouts have exceeded revenue since 2010, but the recent past is nowhere near as grim as the future. According to the latest annual report by Social Security's trustees, the gap between promised benefits and future payroll tax revenue has reached a staggering $59.8 trillion. That gap is $6.8 trillion larger than it was just one year earlier. The biggest driver of that move wasn't Covid-19, but rather a lowering of expected fertility over the coming decades." – Stark Realities

Note the last sentence.

When President Roosevelt first enacted social security in 1935, the intention was to serve as a safety net for older adults. However, at that time, life expectancy was roughly 60 years. Therefore, the expectation was that participants would not be drawing on social security for very long on an actuarial basis. Furthermore, according to the Social Security Administration, roughly 42 workers contributed to the funding pool for each welfare recipient in 1940.

Of course, given that politicians like to use government coffers to buy votes, additional amendments were added to Social Security to expand participation in the program. This included adding domestic labor in 1950 and widows and orphans in 1956. They lowered the retirement age to 62 in 1961 and increased benefits in 1972. Then politicians added more beneficiaries, from disabled people to immigrants, farmers, railroad workers, firefighters, ministers, federal, state, and local government employees, etc.

While politicians and voters continued adding more beneficiaries to the welfare program, workers steadily declined. Today, there are barely 2-workers for each beneficiary. As noted by the Peter G. Peterson Foundation:

"Social Security has been a cornerstone of economic security for almost 90 years, but the program is on unsound footing. Social Security's combined trust funds are projected to be depleted by 2035 — just 13 years from now. A major contributor to the unsustainability of the current Social Security program is that the number of workers contributing to the program is growing more slowly than the number of beneficiaries receiving monthly payments. In 1960, there were 5.1 workers per beneficiary; that ratio has dropped to 2.8 today."