It's mainly because in Chicago at least it's only on Saturday mornings for a very brief period on Channel 21 of the Chicago Access Network.
In any event I blogged about C-Span over the summer. They had this program about the US Capitol in June I believe. It was one of the many specials that I have seen on C-Span over time.
BTW, there's a nice blog list over at C-Span.org. I wonder who determines what blog goes there. I see that one of my favorite video blogs, The Steve Garfield Video Blog is over there. So Mr. Garfield is doing something right. Anyway I have a few suggestions of my own to be put up there at C-Span.