The low bandwidth of audio means that you can jump around with more aplomb and still get a smart foot where you are and if you missed anything, than if it were more information dense. You can also listen to it at 1.2 or 1.5 speed to up the density.
See - that doesn't make sense to me. It's also the difficulty with random access that really annoys me about video tutorials. I can jump down a page of text+images and quickly figure out where to start. If I lose my place in a video I inevitably have to roughly find the spot and listen to some stuff I've already heard.
