And that's because we, Christians, believe that the Word of God is the inerrant, inspired Word of God as The word from The Only God. Why does that matter so much? Did you know that everything naturalistic science holds about origins is based on non-provable theories and interpretations? Regardless of the circumstantial evidence that may be found (like fossils, ice-layers, visible light and stars, etc...), all of these things are not eye-witnesses and must be interpreted in order to have meaning. They are merely circumstantial evidences, not EYE-WITNESSES. But God claims to be the only eyewitness to the Creation. He claims to have been there, to have been the creator, and he therefore claims the only right to interpret the circumstantial evidence we see today. And he interprets this evidence in his Word: the Bible. Furthermore, this God who claimed to be THE eyewitness to Creation was made man and dwelt among us, full of grace and truth: Jesus Christ. The Apostle John testifies as Jesus taught him, that Jesus was there in the beginning and was the means by which all things were created. His testimony, therefore, must stand as eyewitness - not just circumstantial. And his resurrection proves his authority to do so.
So the Christian's reason for responding according to the Faith of Scripture to those who doubt isn't just the propagation of an institutionalized faith - it's not just to further OUR religion. The Christian gives answer to the objections to the Bible because we desire all men to know the TRUTH, because "the truth will set you free." It's not about blind belief, but about the true and absolute reality of the world around us. God claims to be the only eyewitness, and therefore the only one with real authority to interpret the evidence. His interpretation is therefore the actual, absolute truth about who we are, what has happened in time and history, and also what will come.
That's why, in our apologetics and witnessing, the Word of God must always remain the core and focus of our witness - bolstered by logic, God-fearing science, and history, yes, but always through the lens of the Bible.
And here's why: what standard does a naturalistic scientist have to claim that their circumstantial evidence devalues the Bible? They begin by saying that there is no personal, interactive, miracle-working God, so everything in the Bible about such a God must be false. Therefore everything in nature that might point to such a God must have a different answer - an answer apart from God. Therefore they interpret their circumstantial evidences that way. Another evaluater might saw that they don't have any bias to bring towards the evidence, but even if they only bring their own logical reasoning to bear, Scripture tells us that such reasoning in all people is fallen and corrupted and therefore cannot yield the complete truth. We then must be fully aware of our standards and the reasons we have for those standards and we must recognize from where others - not like us - are coming with their standards and reasons. If we are unsteady on our core, we can soon be swayed another way by some other interpretation of the evidence other than our EYEWITNESS: God.