In my own situation, some of my accounts (and some accounts in which my wife was a joint owner) were frozen temporarily because someone at the Social Security Administration (SSA) made a mistake and reported to the financial world in early 2022 that I had died. I wrote about it in this thread.
Last weekend I tried to renew a prescription at my online pharmacy, only to discover that I no longer had pharmacy coverage with my health insurance. When I called the insurance company (Tricare) I was told I no longer had any health insurance coverage at all. I am retired military, so I...
www.early-retirement.org
This kind of error does not happen often but it does happen on occasion. A few months before my situation began, there was a story in the NY Times about this same error happening to an elderly woman living almost entirely on her social security income. A contact at the SSA later told me it happens more than most people realize. While SSA is good at telling the world about the newly and dearly departed, they made zero effort to tell the world when they made mistakes like this, leaving all of the recovery work on the shoulders of their victims. Hopefully this policy has changed since then.
Even after I contacted the customer service folks at all of my financial institutions to explain the situation, and even after being assured the situation was fixed at their financial institution, problems persisted at some financial institutions for several months.
This experience, more than concerns about hack attacks, bank failures and other issues, is why I will never put all of my financial assets into a single financial institution. I will always keep at least a couple of years' worth of expenses at another financial institution. The peace of mind is worth far more to me than any benefits I might be missing if I followed the all-eggs-in-one-basket approach.