Why is everyone responding to the question under the same misinterpretation, that it means "cash" as in "physical banknotes" rather than "electronic Euros"? I know the principle of charity is hard sometimes, but come on.
A) keep the euro notes in their vault, which only works if you deposit paper bills in the first place
B) keep electronic deposits in the ECB and pay interests to do so
In either case if they give back the money to the clients when they ask for it how do you expect them to cover their operating costs (plus the interest they are charged by the central bank in case b)?
Excellent question. There is a company, The Narrow Bank, that has the same idea, but they didn’t get a banking license from the Fed. Matt Levine, whose newsletter you should clearly start reading, has the details: https://www.bloomberg.com/opinion/articles/2018-09-06/fed-re...