lending money at a positive interest rate is doing someone a favor. they need cash, u get some extra for your trouble. at a negative interest rate they are doing *you* a favor similar to paying for a safety deposit box. ur money is safety teleported into the future for a fee.
a house doesn’t keep money b/c it’s not safe. it gives to bank. a bank also can default so stores extra wealth in a big bank. a biggest bank can’t find a better safekeeper. but they can spread out risk by turning it into japanese yen for a fee. (negative yield yen bond)