Dad-films are about men who prove themselves by suffering through a violent ordeal (reluctantly of course ;) ) to protect society. Society is symbolically femine of course. If the wife is dead its a redemption story. On the other hand if the wife is just fine on her own, it sort of undermines the raison d'être of the hero. Like, be normal, your stoic suffering isn't a positive attribute. Society will still be standing if you lighten up.