With that said, if you want anonymity, you don't use a bitcoin bank. Which means you store ALL your money on your computer, probably. Who carries ALL their money in their wallet? No-one.
ATM cards have various protections built into them, pin number, fraud protection, withdrawal limit, the fact that people keep them on their person and know to protect them, etc.
You can't steal an ATM card from 200 feet away without someone knowing about it.
It's also relatively hard to pickpocket people. You have to be right next to them.
The first bitcoin-stealing virus is going to be downright hilarious. (What's your physical analogy there? Someone could build a network of tiny robots and have them covertly steal cash from banks? It's theoretically possible.)