Personal reasons, ie he wants to play with his dog. And see his family. I could be wrong and if it's something wrong, I'd be embarrassed but that's the way it seems with him.
You know what - that's fine. No one can ever begrudge him that. But give the game up. You're contracted by NZC and part of that is making yourself available for your province. Otherwise you're just going through the motions to keep the pay rolling in.