It doesn't, obviously, and I never said it did. It prevents the camera from being used to surreptitiously record useful information when a machine has been remotely compromised. It's the same reason nothing with a transmitter is permitted in classified areas without specific authorization. Preventing a remote takeover is effectively impossible, but these steps reduce the usefulness of such an action (which is part of the defense against them).

Physical controls can be as effective as technical.