The reason for that timecode start is for broadcasters. Any tape submitted for broadcast must start at 1:00:00;00. The network spec may call for the projects to have 50 seconds of color bars, 6 seconds of slate and 4 seconds of black preceeding the first frame of the actual show, so the actual show can't start at 0:00:00;00 or else the leader would be negative, which wouldn't be good.
Can someone please explain to me why the FCP Timeline starts out at 1:00:00:00 instead of 0:00:00:00 ?