NBC, I believe, has all events in individual feeds. You chose what to watch, you can't show everything in prime time hours or introduce everyone to everything. That technology wasn't around when ABC had the coverage.
Elsewhere: http://summergames.ap.org/article/8-years-later-athens-olympic-venues-decay
These are two stories which show that the system fails periodically. How you convince future organizations to correct these matter is now taking recommendations.