Storing money costs money: at least the bank fees, if not the negative interest rates. Processing money costs even more money: operations must be scrutinized,

Storing money costs money: at least the bank fees, if not the negative interest rates. Processing money costs even more money: operations must be scrutinized, international movements require validation and communication, and various AML/CFT/Fraud procedures must perform investigations etc. You have accounts in various currencies, perform conversions to maintain liquidity… So I can see why they would start dipping their toes into investments. Once they start, they probably don’t consider enforcing Basel III to their procedures, and things just unfold.