Simply put, if I cannot perceive something in any possible way, it must not exist.
For example. I cannot see bacteria with my naked eye, but with a microscope. I've never seen a dinosaur, but I've seen its bones. Etc.
God, on the other hand, I have never seen, or perceived in any other way with any of the 5 senses. Therefore, he does not exist.
Secondly, scientifics aside, it is a well known fact that throughout the ages, religion has been used as a tool, whether it be for disciplining children, scamming ignorant peasants, what have you. Why should Christianity be any different? The only thing Christans have to give them any possible notion of a god is an old dusty book, which has been edited, added to, and rewritten hundreds of times by dozens of groups of people.
The point being, I can't see God, the evidence for God is slight at best, and with all of the inconsistencies in the bible, there really is absolutely no reason to believe in God. The only people who believe in God are those who are afraid of death, those who are brought up in a Christian household and effectively brainwashed, or those who just like thinking there's someone watching out for them, when there really isn't. I myself happen to be one of the lucky ones, who despite the effective brain washing, turned out to be a fully functional human being, without the hindrances of false prophets lurking in the back of my mind.