I will add that Social Security retirement benefits are federally taxable (state taxable in some cases) up to 85% of the benefit depending on the amount of other income. You have already paid federal and state taxes on YOUR portion all those years when the SS tax was withheld from your paycheck. You are now being taxed twice on this money. Some people don’t agree that the money is double taxed but that’s their opinion.
I am one of the ones who do not agree that it is double taxed. First, 1/2 of the original contribution was definitely not taxed if a person was employed, because the employer paid 1/2 of the original contribution, and the employer got to deduct it as a business/payroll expense. Even a self employed person gets to deduct 1/2 of the original contribution so 1/2 of their original contribution can't count as double taxed either. Then, 15% of the benefit is never taxed, which for many people would be about the amount they originally contributed. What ends up getting taxed for some people, is, at most, the growth, which wasn't previously taxed because it wasn't previously treated as income.
On top of that not everyone pays any tax on their SS benefits. People who have only SS benefits for retirement or small pensions/small investments plus SS benefits don't pay any tax at all on their SS benefits. Some people pay tax on a tiny percentage of their SS benefits with others gradually working up to the 85% you mentioned if their other income is high enough.
Therefore, you will never get me to agree that it is double taxed for the majority of people. There might be a few people who have relatively high other retirement income, who end up dying fairly young, who might have gotten double taxation on a portion of their benefits, but that is going to be a relative few.
The 15% that is never taxed is going to cover the 1/2 of the original contributions for the people who live normal lifetimes.