Having someone look directly at the camera can sometimes feel unnerving in video. Also it's a good way to hide a teleprompter and the side-to-side eye movement
I'm not sure about unnerving. Psychologically, I know I'm looking at a recording. But when they're not looking at the viewer, it looks like they've got better things to do.
I see this being used all the time recently, including on large productions. I assumed it's meant to convey the feeling of talking with someone who may also be talking to others. But it gives me hives (for which I'm losing points, but what can I say).