Why is the creation story so important?

Because to those who believe in Creation, it is how their life began on earth.

The Torah creation-account, unlike various ancient stories, does not attribute creation to a multitude of warring, flawed deities and their demigod offspring. In addition, the Torah account makes human responsibility foremost, stressing the lesson that the world is not a happy-go-lucky place in which people may cavort unthinkingly; and nor is it a melancholy accident whose existence is ultimately purposeless.