I haven't made a detailed study of the topic, if you really want to know you should research it.
However, my understanding is that prior to the creation of Social Security, the aged and infirm were often living in horrible conditions because they were no longer able to make income to take care of themselves and hadn't saved sufficiently to support themselves in old age.
Hence the establishment of Social Security, to alleviate this suffering. Most Americans, even today, save only a small fraction (if any) of their income for a "rainy day". When the paychecks stop coming, without Social Security, their situation gets quite dire.
However, with Social Security and better health care, fewer kids, and other Government mandated savings programs, the "old" demographic has become the richest, by and large, in the USA.
Personally I think it is time to stem the tide of wealth transfer from the now-poorer, younger demographics to the richest demographic (robbing from the poor to give to the rich) by raising the retirement age, ending the wage cap on social security tax, making the benefits taxable above a certain income threshold, and lowering the social security tax on the folks who are still working.
I don't think it makes much sense to have a Government program to make the most rich even richer at the expense of the poorer.
As for the social security recipients who will cry about this, well, take some responsbility. YOU voted in the Governments who spent the social security surplus into broader Government debt, now YOU can live with reduced benefits.
--PeterM