What I don't understand is why do banks work this way? Imagine you were designing the bank from scratch having no knowledge of the current banking system. How would you do it? The most obvious thing would be if a customer deposits money, you would hold 100% of the money 1 to 1 exactly how they deposited it. Then the bank could make money by providing services to their customers. If I had to bet, most people who have…
Now imagine you've finally settled on a cost structure that can pay all of your insurance, operating costs, payroll, and everything else. You charge monthly fees and you might also charge per-interaction fees to do anything or talk to anyone.
Then a competitor comes along that operates in a fractional reserve manner. They not only offer zero fees, they actually pay customers interest to keep their money in the bank. There is a risk of failure, but it's rare and all evidence points to customers not suffering massive losses when it does happen due to various regulations. Inconvenient, yes, but it's unlikely that you're going to lose all of your money.
The majority of your customers would leave for the competitor bank.