Why do so few universities offer OpenCourseWare videos of their lessons?
Making an OpenCourseWare course isn't as simple as getting a team of kids with videocameras and uploading the course onto YouTube. There is a surprisingly high standard that the Professor and the University attempts to meet when they prepare a course to be deposited onto OpenCourseWare.

Stanford had built entire classrooms for the purpose of sharing online classes. Many of them have 3-4 cameras controlled by two operators while another is entirely responsible for the sound. Classes that require a balance between boardwork, slides, and discussion require a very well-trained team of videographers to recognize what they are supposed to be looking at without breaking the rhythm of the course and capturing the intent of the lecturer. 

Ask any Professor how prepared their lectures are. Despite how absent-minded most professors seem, there is a large amount of practice and slidology behind each lecture. OCW adds a whole other layer to preparation since the course actually has to run on schedule and conclude with the course completed. The materials used require additional thought since OCW is limited to only a single camera. Look at some of Yale's early OTC courses; the professor will make references to a figure and the camera will be focused on his gestures rather than the actual information that they are trying to portray.

Lastly online courses are extremely expensive and don't truly make the return on investment as one would imagine. For instance, Utah State was forced to end their OpenCourseWare initiative.