Maybe he's just plain happier devoting his limited talents to attack ads.
The Chalk River nuclear installation is down again. Heavy water leaks. Let's see, the Chalk River facility has been beset by massive problems for two years. That's all been on Harper's watch. It's still screwed up. He fired Keene when he needed a scapegoat but those only come in ones and there is no ducking the scandal this time. Steve has to wear this one.
Atomic Energy Canada, or more correctly, Steve's Atomic Energy Canada has shut down the reactor so it can take a month to figure out what to do. In the meantime that reactor won't be producing isotopes which will leave radiology in a bad way in central and eastern Canada.
Steve's own beloved Alberta, however, apparently knows better than to trust the Harper government to supply isotopes. It gets its supply from Europe. Oh, I guess that explains why Harper could care less.