> If this technology was refined, you'd just use this system to send secure messages without the need for an encryption key.

As far as I know, I don't think that meshes with what actually happens. This has nothing to do with the message being secure; anyone with all the pieces could read the message.

The important part is, since observation effects quantum state, the receiver can determine whether a third party observed the key. If the key matches, then there's a guarantee that it was not observed, and therefore is safe to use.