The analogy doesn't work perfectly because there is usually no cost to withdrawing and depositing cash from an ATM. And when there is a fee, it tends to be fixe

The analogy doesn't work perfectly because there is usually no cost to withdrawing and depositing cash from an ATM. And when there is a fee, it tends to be fixed as opposed to percentage-based. These may very well be solveable problems, but there's definitely a bit of work to do to make bitcoins function like pocket cash.