It's because they've been allowed to control the room. Again, Spicer seems unable to control the room, and that's kinda his job. He is not the first Press Secretary to face "hostile" reporters. Restricting information output seems to be the wrong direction we need to be traveling.
No cameras means the information can't get out?
The media is feeding off of the behavior. Everybody in there is trying to make a name for themselves.
It's sort of like spreading the name of a killer, it's what they want.