Why do Christians quote Bible scripture to argue their point?

Belief or lack of belief does nothing to change reality. The bible is the inspired Word of God, this is proven by historical accuracy, fulfilled prophecy, and many other facts. How "irrefutable" is your evidence, in reality? Scientific theories are just that, theories, they will be updated and changed or thrown out within decades if not sooner. Not only that, but how can you actually trust the word of man? You believe it because its written in a book...