I think the OP has raised a good point about online accounts.
Think of bank accounts, there are around 7 yrs of statements accessible, if a bank closes that due to death, then those records are unavailable.
In the old days, everyone got paper mailed statements, so generally they were available post death.
The past records might be important should a financial error/question/etc arise from one of the heirs, or a creditor (like was the debt paid off).
Hopefully banks/stock brokerages/etc don't delete account access, as I could see the desire to look up old records.
I don't know if SS has some records as well.