Financial institutions (banks) are responsible in handling financial issues, records, accounts and income of individuals, companies, churches and organizations. They respond promptly according to your demands on your accounts, they also have zero tolerance for fraud and are very security conscious, security intelligence and anti financial crime expertise but they've policies of not collecting dime from customers accounts yet banks are most wealthiest institutions on earth.
I want to ask a question to people who have a large amount of savings in the bank, come and don't say beforehand that you want to withdraw all the savings you. See how their employees react? I believe in their safe there is no cash that can be given directly to you and they have to call the center to get the money to the branch. That's how they manage the customer's money and I also remember how the bank only keeps the total value of your money but they never keep the physical amount in their safe. There are many problems with this system and it is like a cash cow that will continue to drive human dependency.
I don't want to get into how they make their money because they are a financial institution and automatically there are many ways for them to make a profit. If you are from Nigeria, have you ever experienced a time when your fiat currency was scarce and not accessible to services when you wanted to withdraw money and I remember a post from my Nigerian friend saying they were short of physical cash in the bank resulting in long queues at that time.