Specifically, reality competition shows where each season has a group of contestants competing for one prize such as Survivor, The Amazing Race, Big Brother, and American Idol.

America's Next Top Model is probably the only one outside of Bravo's original reality shows that had any mileage on cable syndication. It has enjoyed several years of marathon seasons airing on VH1/Oxygen/Bravo.

Older seasons of Survivor only got a few seasons aired on Outdoor Life Network before disappearing completely. This also happened with The Amazing Race on Travel Channel.

American Idol did have a syndicated retrospective show called American Idol Rewind that showed clips of older seasons and even spoke with some contestants years after they were on. But even that faded pretty quickly.

Probably because if people know who's going to win, they lose interest in the reruns; likewise soap opera reruns don't seem to do well either, because people won't watch if they know what will happen next. At least with sitcom reruns where people already know the plot, they won't remember all of the jokes.