You must distinguish technical correctness criteria from real-world systems requirements.
Certainly banks must be able to account for every withdrawal and deposit, and more generally for every in and out on their balance sheets. That's what regulators are for. But no regulator will ever hold a bank to prove that the accounts were completely "consistent" at any given point in time, particularly if it's long in the past. That's why banks can get away with deducting sums from your account while not crediting the recipient until days later, as long as they keep track of where everything has to go eventually.
In their own trades, modern banks are capable of millisecond-accurate accounting, so obviously this is not a technical limitation. The simple truth is that there is an incentive for the bank to execute deductions as early as possible, and credits as late as possible, because that earns them more fees that doing the opposite, and as long as there is no legislation which forbids this, they have no reason to improve. So 'eventual consistency' in banking is not a technical compromise for lack of a better alternative, as with huge NoSQL data stores - it is plain and simple good business for the money handlers.