I can only assume that either you've been unlucky, or I've been lucky. Most of the videos I've purchased have been excellent and high quality. The videos are generally short and to the point. 5-10 minutes covering a specific topic. This also means I can move at my pace. Couple that with speeding up the video to get through certain parts faster, it's an wonderful choice.

Be careful you aren't looking at presentations in video format as an example of video for learning. It's not.