First, check out this amazing video. You might have seen it before, but watch it again anyway: http://www.youtube.com/watch?v=_ve4M4UsJQo&feature=search
Now, God could have just walked over to the car and switched it on, metaphorically speaking. But how much more amazing and awe-inspiring to do it this way!
Similarly, he absolutely has the power to speak and have the universe appear just as it is: but how much more amazing and awe-inspiring to speak it all in potentia in the one great word of the Big Bang, and then have all the parts connect in precise, incredible ways over nearly 14 billion years of connections to have us here to marvel at it all.