There is no doubt that TV News Reporters knock on a lot of doors and often times they like to do it on camera.
Have you ever seen a TV Reporter knock on a door on camera and someone opens the door?
Nope. The door knocking stunt is done mainly to fill time in a package when the Reporter can't find the person they are trying to interview.
Jimmy Kimmel has put together a montage of Reporters knocking on doors.