The SS benefit formula currently has 3 tiers: 90% of your former wage, 32% of your former wage, and 15% of your former wage up to the SS-taxed maximum. Which for 2023 is $160,200.
So much like income taxes in reverse, the relatively poor get a real good deal and the very highly paid get a less-good deal. Someone who was always in the lowest wage bracket would receive a benefit of 90% of their pre-retirement wages, whereas someone who earned exactly the SS max every year would get ~25% (a blend of the 90%, 32%, and 15% brackets) of their pre-retirement wages.
Under current law, someone who’s wages are more than the SS maximum each year pays no extra tax on those extra wages and and gets no extra benefit as well.
Changing that so they pay more tax but get no more benefit changes SS from an admittedly re-distributionist, but still you-pay-in/you-get-out system to one that is simply “A tax on me given to you”. In other words, welfare.
Which is a dirty word in the USA. There will be a very different sort of pushback if the SS wage cap for tax is raised with no SS benefit increase to go along.
As to my second point, I suspect you misunderstand what I meant. I did not say that very well.
Various commentators look at people like my exemplar $3.5M executive and think that if we eliminated the SS wage tax cap then $3.5M times the SS tax rate would flow into the system. Nope. It’d be $500K times the SS tax rate coming in. Compared to $160.2K times the SS tax rate under 2023 law. So the bump in SS-taxable value would be ~$340K, not $3.34M.
As most high earners / rich people / fatcats derive rather little of their income from wages, any projection that ignores this difference is at risk of overstating the gains to be made by a very significant factor. Said another way, in our highly unequal society, just looking at gross household incomes is a very bad proxy for gross household wages.
SS is and always has been all about wages and only wages. Both at the taxing end and at the benefit end. It (partially) replaces your wage paycheck, not your savings / investment earnings. Be the former or the latter great or small.
Of course one could simply change the system by deciding all income of all sorts is subject to SS tax. But once again that is a significant ideological change that will bring out a very different sort of opposition. That can of worms can be opened. But it would be a political / policy mistake to assume it doesn’t exist then be surprised when the worms spring forth.