Because you can&#x27;t buy $1 billion in individual cash saving accounts; there isn&#x27;t a supply of them and a bank won&#x27;t sell them to you. When you have very large sums your options of what you can buy and kind of the returns you can expect change. A small investor with $10k can experience greater volatility in their returns (good and poor), and can just go ahead and buy Apple shares without the FT writing an article about it.<p>Also, the base rate is only really encountered directly by Banks that have accounts with central, in the case of the US, or regional central banks. A normal company and even very large non-bank firms don&#x27;t typically have accounts with the central bank. For consumers and most businesses the interest rate set by the fed is more of a benchmark that ends up being used to help calculate the returns of other products.