Security is hard. If you're going to encrypt something, the first thing you have to work out is how you're going to manage the keys. More to the point, if you expect them to be managed by a human, that means coming up with some way for people to remember or otherwise manage them. And that means passwords. Passwords are an awful solution to security, and having a USB mass storage device that demands a key be presented means requiring some sort of user interface for that.

Orthrus is a way to do truly world-class encryption without any key management at all, because the key material is automatically spread between the two cards. The security solution is trivial. Got both cards? You have access. Got fewer? None for you.