I think that it tied Vader to him for as long as it did. Why would an all powerful self-serving Sith serve an inferior master for so long? If he had the hope that she was alive and sought her out, or if she was alive, he would have tried to grant her the government she dreamed of in episode II. If he found her dead and the kids, he would have had reason to live for himself and them and would again have taken down the emperor in his own rise to power.
But crushed like that, betrayed by all, and stripped of everything, he became naught but the hound of the Emperor until his son gave him something he cared about again. And he destroys the Emperor... The Emperor is doomed in any situation that Anakin has something to live for.