Photographers are kept out of the room during live presidential telecasts, because the sounds of their cameras distracts from the audio. This is standard practice.

As President Obama continued his nine-minute address in front of just one main network camera, the photographers were held outside the room by staff and asked to remain completely silent. Once Obama was off the air, we were escorted in front of that teleprompter and the President then re-enacted the walk-out and first 30 seconds of the statement for us.

via Ready to record history | Photographers.