Make-Believe Belief
I think a lot of people say they believe in God because they think they are supposed to, not because they really do. Many times, it comes out as a half-hearted mumble like, "I don't go to church, but y'know, I believe in God and stuff."
There's a lot of cultural pressure in the US to keep making believe you believe. It's perceived as the norm, the socially acceptable default position. Such a perfunctory declaration like the one above means, I think, that the person making it is uncomfortable and would really rather not talk about it anymore. What they mean is, "Look, I'm saying what I'm supposed to say, now please stop asking questions."
The fact is, in this country, saying you don't believe can cause you a lot of problems; with your family, your friends, even at work and with police and government in many places, even though religious discrimination is patently against the law. http://www.youtube.com/watch?v=tiyJzWy3CDQ
Really, for a lot of people, religion plays very little part in their day-to-day lives most of the time. They may go to church on Easter or Christmas, but the rest of the year they can't be bothered. Even for people who do attend church regularly and believe with a bit more conviction, they live most of their lives as we atheists do. They use reason and evidence to make decisions about their lives. They go to doctors, they buy insurance. They're properly skeptical about marketing claims, used car salesmen, things like UFOs and ouija boards, the Tooth Fairy and Santa Claus, and of course about every other religion except theirs. But when it comes to their own religion, they dutifully parrot back the appropriate platitude, perhaps with some kind of within-the-rules qualifications.
I think many people go through life as perfunctory or make-believe believers because they don't want to be perceived as (gasp) atheists who have a very bad, but largely fabricated and undeserved reputation, a caricature, if you will. This caricature was created and tuned over the years by the leaders of faiths to keep people coming to church, paying their tithes and keeping them in business and employed.
People frequently seem genuinely surprised when I tell them I'm an atheist. They usually don't say it, but I can tell they're thinking, "But he seems so nice." That's because they have never met a real, live atheist-and this is important-that they knew was an atheist. As I've pointed out, being an "out" atheist has definite downsides, especially in certain highly religious parts of the country. People who don't believe don't generally talk about it, because even the actual existence of an atheist is considered "offensive" to the faithful.
So religion has managed to get this kind of perpetual motion machine going where they construct a strawman atheist that they imbue with all kinds of mean and evil qualities and then tell their flock the tale, selecting appropriate scriptural references to back it up. Of course, very few people jump at the chance to be vilified, so they don't identify as atheists. They may even go so far as to play the make-believe belief game just to be able to get on with their lives. So, since nobody will admit to even questioning their belief, never mind being an atheist, the faithful flock never actually have to confront the cognitive dissonance that the nice guy who fixes their car, or the doctor that makes them well, or the kind teacher that teaches their kids algebra is a non-believer. So the caricature is never challenged, so non-believers stay in the closet, and so on ad infinitum.
The misinformation propagated about atheists is manifest in ways that range from the truly vitriolic and mean-spirited to the comically naive. There are many very nice people who, having never met an out atheist, harbor the most outrageous beliefs about atheism that you can tell stick in their craw when they actually have to say it in front of someone who doesn't shrink from the apellation.
So if you don't believe, it's important to say so because it makes the prejudiced confront their cognitive dissonance and at the same time shows the perfunctory or make-believe believers that it's ok to not believe and that perfectly normal and nice people that they know and like and trust are good without gods. It's what Daniel Dennett calls "breaking the spell" and a big part of that spell is its attendant voodoo doll character of the atheist. It's not true and it never has been. So go forth and identify, brothers and sisters!