You may have fallen prey to anthropomorphism here. We're so used to man-made constructions that when we see something that we did not build, we tend to attribute its existence to an entity which is conveniently like us.

What did you mean by "creator"? From what I can see: us, or God. So, what we did not create (like the complexity of life), must have been created by God.

But what did you mean by "God"? Most of the time, God is refereed to as an infinitely smart, infinitely potent, utterly incomprehensible entity ("the ways of God are impenetrable"), which is very much like us ("he made us in his image"). In other words, magic with a personality.

I have a problem with magic: it explains everything, by explaining nothing. It's what in http://lesswrong.com they call a "curiosity stopper". In the face of magic (or God), I feel like a balrog before Gandalf: I cannot pass. It's very frustrating, because I'm naturally curious.

And to a point, I can satisfy my curiosity. For instance, the creator the complexity of life is evolution (skipping very very long explanation that I don't fully understand). The creator of evolution is the laws of physics, whose creator is… I don't know. For now the buck stops there. It doesn't mean, however that it should stick there. That would be freezing the current boundaries of our knowledge. If I replace "I don't know" by "God", I forbid myself to look further. Maybe there isn't anything further, but that I don't know.

So, you don't "know" there's a creator. You just marvel at the mystery of the creation. You don't want to really explain the creation, for it's precious mystery would be gone. Or you are just uncomfortable with uncertainty, so you tell yourself a story where the scariest uncertainties are easily explained.

Or you just didn't think this through. Yet.