I hope I'm not making a crazy statement to say that people in general aren't that great at security. Unless you have the wisdom to keep your wallets offline or secured with a password longer than 20+ (or whatever) charactes, it's only a matter of time before a worm or virus gathers up hundreds of insecure wallets.
Secondly, there's nothing intrinsically wrong with banks. Banks help the supply of money and keep economies going through investment. Banks can build green addresses for instant purchases which Bitcoin needs to be successful.
Bitcoin wasn't designed to get rid of banks. Bitcoin was designed to give banks and people a common way of transferring money without expensive accounting auditing, secret protocols, and government centralization.