It is also one way to obscure the fact that someone's using a teleprompter because it is more difficult to see that their eyes are moving back and forth.
From what I watched of the presentation, there was also a fair bit of moving around. In my studio, we primarily used it as a way to hide main camera adjustments in the edit, usually from the interviewee changing positions, slouching, etc. Generally, a high enough quality production will never rely on a single camera regardless.