Though there is plenty of evidence for age of earth, why are people still wasting time with creationism?

The point is that the only evidence that supports the Earth being 6000 years old is a book. Now figure that the book is supposed to be right about everything, and that if anything is wrong in it, everything else within it has the chance of being discredited or false. So if theres proof that the Earth is older than 6000 years old, that is a threat to what the rest of the bible says.