Because there is no evidence the creation happened the way the bible says it did.
Would it shock you to learn that the first few chapters of the book of Genesis is not a text of modern science?
It is a collection of allegories with a moral purpose to them and that is all they were intended to be. The people of the time had no concept of modern science, so to interpret them as such is to misread them.
I think that there are some scientific facts contained in Genesis but it is speculative of anyone to assert that the text in Genesis proves anything about science, in fact I think that is again a misinterpretation of the book.
There seems to be a record of the recovery of the Earth from a recent catastrophic event, if you note how in verse one the narrative starts with the existence of the Earth the stars and heavens. Then it presents a story of a recovery in which light is restored to the surface, at first weakly and diffused, then in stronger amounts of direct sunlight. Then life comes about in the oceans, then plant life flourishes on the surface, and then the animals come along. I suspect that the first few chapters of Genesis are recorded oral history from the small handful of human beings that survived the Toba catastrophe.
But that too is speculation and to suggest it is more than that is to, again, misread the book. It is not a book about scientific fact, but of moral fact.