Why does all timecode start at 1 hour? (01:00:00:00) Is there a reason timecode in Final Cut 7 and timecode in Pro Tools starts at the 1 hour mark? eg. 01:00:00:00? As opposed to all zeros? Some old broadcast standard that I don't know about?
It's to leave room before first picture, for slates, countdowns, test signals etc, while still preserving an easy count of running time for the video. Yes, it traces historically to broadcast and in particular videotape.

Many tape-based editing systems couldn't deal with 24-hour wraparound, so the next even hour became traditional 'time zero'. I suspect that most non-linear systems are the same.