The problem is that those high profile incidents can spiral out of control, and suddenly shells are raining over Seoul and the SK/US army is swarming across the border. If that happens, it's nice to be able to still threaten. I'm not saying it's likely, just that NK is not crazy to want nukes.
Also, I don't see China benefiting from NKs belligerence, it's more a price they are willing to pay for the reasons I mentioned in my previous post.
Checking out seems not to do much.