Because you don't want to be at the mercy of a bank? When your money sits in a bank account, anybody who wants to take it, or seize it, simply has to contact the bank with appropriate legal authority, and poof - your money is gone, with no recourse whatsoever. At least when you have the physical cash, they have to deal with you personally.

Of course, as we see here, that's becoming more common.

Maybe banks are less easy to trust where you are. I have concerns about what happens with my records, but no concerns over my money going away. All banks in New Zealand have a pretty good health rating.

People feel that way about their banks until the first time money is taken out of their account without their permission. Certainly very possible in the United States.

People generally don't carry large sums of cash, but there are a number of cases where one might.

People who are paranoid about banks, for example, or people who cannot, for one reason or another, use a bank account without raising eyebrows.

Possibly the most innocuous example I can think of would be someone who is paid mostly in cash tips, and does not put them in the bank to avoid any paper trail requiring taxes. If they then paid their living expenses entirely out of their "base" wages, they could accumulate a substantial under-the-table pile of money.