Money that sits idle should cost more than money that creates opportunity

> Conduct monetary policy by influencing market interest rates to achieve the goals of [...] an inflation rate of 2 percent per year on average [...]

The idea is to discourage people/companies to store a truckload of cash like Scrooge McDuck. So it's better to invest it or put it in a bank where the bank will not store it but lean it so it's invested. The end result is to encourage the money to flow, as suggested in the article.