Currently, contributions to 401k or equivalent are "pre-tax", directly reducing taxable income in the US. The deduction reduces taxes at a person's highest marginal tax rate.

The Bıdɛn administration claims this deduction benefits high income earners more than low income earners. (That is, someone at a 37% tax rate gets 37% benefit, while someone at a 12% tax rate only gets 12% benefit.) They are proposing changing the deduction to a fixed 26% tax credit for everyone. A 26% credit benefits anyone with a marginal tax rate below about 20.6% but hurts those with higher marginal tax rates. (And so creates some incentive for high income earneers to use a Roth IRA instead but that's a different issue).

It wouldn't be much of a stretch to call this a wealth redistribution.

The argument also neglects two key benefits that already exist for low income earners:
- A low tax rate makes after-tax Roth contributions very attractive
- Low income earners (up to about $33k single or $66k married in 2021) can get the Retirement Savers Credit, which is on top of the other tax benefits of IRA/Roth.

I also have heard the Biden wants to make changes in Social Security. So far, he has not spelled out the particulars.

I remember back in the Jimmy Carter Administration the last check you get after you died would go to funeral expenses
and it was changed.
Now, once the death is reported the Social Security stops any further checks and if it paid will have to be returned by
the banks.

Carter called the payment of the last social security check for funeral expenses obsolete.