It's also a bad comparison for another reason. Bank holds limited goods. I.e. even if robbers break the security, they'll just get those goods, and all other robbers will have to go through breaking in again when they decide to rob it. That actually deters most of them.

Digital content is easily duplicatable. When DRM is broken, pirates redistribute it to all others without limit. In the bank analogy (to make it comparable), it's like becoming an infinite fake bank, so all subsequent criminals don't need to rob the original bank anymore, but can take from that secondary source as much as they want to. That's exactly what makes DRM completely irrelevant in reducing piracy.