Bitcoin makes a difference between storing money and lending money. If you want to store your money, you just make a backup of your wallet, possibly encrypted, to a safe place. It's clearly distinguishable from giving the control of your money to an investment bank which lends them for interest. In the mainstream bank system it's different: you deposit 1000$, the bank lends 900$ of it to someone but still shows 1000$ as your balance, and so the money supply is inflated.