I'm not sure what the disconnect is here. It's not Chase's money sitting in reserve drawing 0.5% interest. It's your money. Chase makes money for free by just holding your money. There are certainly expenses associated with running a bank. Those expenses don't significantly increase for Chase if you deposit an extra $100K in your savings account, but Chase will make an extra $4K just for holding it.

I'm not sure if you're under the impression that I'm claiming that holding reserves is the primary way banks make money. I'm not. The discussion about reserves is to answer the claim that a dollar deposited with Chase will automatically result in a 90 cent loan to someone else. It will not.