Quote - "if a person cannot hear the narrative you still have the video image to follow.  Is that not acceptable?"

If the topic of the video is familiar to the viewer, then the audio may not be extremely important. But if the person is a newbie to the theme, then the audio is normally very important. Do this experience: pick a theme you're not familiar with, search for a video tut about it, watch it with muted audio and judge by yourself.

Quote - "I hope you understand and are still able to "limp" along with just the video."

Don't forget that many people can not watch videos. I think that was what jugoth was talking about. There are several diseases associated with watching videos. See this one, just as an example:
http://en.wikipedia.org/wiki/Photosensitive_epilepsy