[explorerjenny]

I just learned (thanks to James Arlen who commented directly under the blogpost), that Flow B was really useful when ATMs first showed up in the mid-80s, because people mostly made more than one transaction. They quite often made deposits and a withdrawal within one process and for each action the machine had to read the card. Therefore, it made sense that the machine kept the card till the moment when every single action was finished. But this isn’t a common pattern any longer and the flow should change in a way that makes more sense nowadays.