Because Reed is Reed. We've seen his best, and even though he can be caught out every now and again, he's the definition of solid. There is no point in demoting him, because you can't get blood out of a stone, he's never going to just turn in to a superstar. But even at his worst, he's better than Copley was last week, at least in terms of jeapardising the entire defensive line.
Copley was a liability last week. He let in more tries in one game than Reed has all year. He's too big a risk right now to simply persevere with in the NRL team. Unlike a Steve Michaels though, there is a great ****ing footballer in there, and it's only going to take some subtle things to turn that around. What's better than being able to give him real match situations for him to work with, in his preferred position, with absolutely zero risk to the fortunes of the NRL team? It makes perfect sense to me. Sure it's a step down in terms of quality of opposition, but think of it as playing a really tough video game at an 80% speed setting to prime yourself for the real deal.