You do realize that recording video content was inherently created /after/ the ability to transmit it in the first place, so even if looping has been around for a long time, the ability to transmit video has been around longer. And, as the other reference mentioned, much longer. The point of these systems was to be an alternate to a failure, so it failing wouldn't be acceptable - and rewinding or even replacing with a second tape would be a failure of a system that has to constantly present an image to the viewer.