There is significantly more planning behind video than most still photography. Scenes are story-boarded, shots are carefully set up, lighting is adjusted, etc.
When you look at video that was not carefully planned the ratio of hours shot to hours used goes way up. The Blair Witch Project had a ratio of about 12:1 and while the video from that film was effective it was hardly outstanding from an artistic point of view. Shot-on-location documentaries like Happy People or Welcome to Leith have similar ratios. Even though they're carefully shot, the ad-hoc nature of collecting footage for a film like that makes it necessary to amass a huge amount.
