Why good? Well, before I answer that, I should point out that Hawking also said that he couldn't prove Heaven wasn't there, which is honest of him. Considering that Heaven, should it exist, is a metaphysical location, should Dr. Hawking find anything resembling Heaven, I would be seriously worried.
It's sort of like if someone could point to a box and say "There's God."
I'm sorry, but for something to claim to be my deity, it would have to be unlimited in scope... ie: God doesn't fit in a box.
Besides, Hawking is not in the religion business, no matter how many ways he tries to interject himself into the matter. Were he to fall back on a supernatural explanation for anything, that would be bad science. God doesn't fit into an equation, can't be experimented on, tested, retested, or submitted to any version of any scientific method.
For example, there's the Big Bang. There is evidence for such an explosion to kick-start the universe. Communications satellites have picked up signals that are, in essence, "echoes" of the Big Bang. However, the amount of things that we know about the big bang aren't accurate; most of what we know about it is supposition. People have theorized about what happened based on the results: as in "in order for X to have happened, Y must have occured at Z seconds within the event itself."
If any scientist says "We think there's a God, because we can't figure it out otherwise," that is a cheat. That isn't science. The best a scientist can get away with is "It looks like a bloody miracle, but give us time, we'll figure it out." Using God as a placeholder in a theory is cheating.
However, in the case of Hawking, I object when he injects his atheism into his science.
Hawking has come up with several theories on how the universe started; from what I can recall, all of them throw out the Big Bang. I think the simplest way for me to explain it would be to say that the universe is a self-sustaining temporal loop where the Universe simply goes and starts itself repeatedly...
I think I heard that theory on Star Trek once, only they made it sound more believable.
Self-sustaining temporal loops? Really? It's a theory that tosses out a basic principle of science, namely "cause and effect." It's a theory that has no evidence, and not even his mechanical voice box can make me believe it. It's bad science. Why would Hawking say something so stupid?
The sad thing is, the only reason I could come up with is that, if there is an effect, like the Big Bang, there must be a cause. And, right now, the best guess could be, hmm, God.
A suggestion to Dr. Hawking: make a better guess. You've thrown out what scant evidence there is that points to the origin of the universe, and you've stolen a plotline from a science fiction show for a replacement theory. Fail. You're a physicist trying to deal in metaphysics. Major Fail. You should not be able to succeed. If you are honestly putting mental energy into this, you do have better things to do with your life.
Seriously, if a PhD in philosophy tried to pass himself off as an expert in quantum physics, he would be laughed off the stage. Why Hawking thinks he can get away with the reverse is beyond me. Even Hawking's (Catholic) wife told him, "Oh, Stephen, leave God alone."
And, should Hawking find a place and call it Heaven, I'll believe that like I believed the rapture would come last Saturday. And how did that work out for everyone?
Anyway ... I think the below is a better use of science than Hawking wasting his time "disproving God." And, this is a lot cooler.