Many people, especially religious pundits who want to knock "cold, logical science" down a few notches, claim that science is as faith-based as religion. I would tend to agree. Those who disagree argue that science relies on painstaking experimental method and proof to back up its theories--which is true, but only to a certain extent. When it comes to the things that science just can't determine (or at least hasn't determined yet), we depend utterly on faith.
A specific example of why scientists are illogical, however, is evident: the afterlife (or lack thereof). When you die, if any of the major religions are correct, you proceed to some sort of afterlife. If you're an atheist, you believe (mmm, sounds faith-based) that there is no afterlife. Or at least, there's no afterlife with God in it.
But here's the clincher: if a "God" does exist, then you are screwed--at least according to those religions again, since the non-believer infidels usually enjoy a fate such as being "consigned to suffer the flames of Hell for all eternity". :fear: Nicer religions stick them in limbo or some such dimension like that. What it comes down to is: believers prosper, non-believers don't.
So, logically, doesn't it make more sense to believe in God? Hedge your bets. If God doesn't exist, like you initially thought, but you've pretended God exists all your life, then you lose nothing. You don't exist anymore, so you won't be around to figure that out. On the other hand, if God does exist, you lose nothing, because you've spent your life believing in God. Win-win. ^_^
I realize that this oversimplifies it. You do have a good probability of choosing the wrong religion in particular; I'm not saying that this is a no-risk prospect. I also realize that this is not an original idea (I believe that I first heard it from Pascal, but his mind was warped by others anyway).
So those scientists who are atheists claim that they don't believe in God because there's no proof God exists--it's not logical to believe in something without proof, eh? There's some religious scientists too, who think science and religion can co-exist peacefully, and I tend to agree with them. It is not a one or the other type of argument, and I wish that polarized extremists would stop attempting to reduce it down to such.
Life just isn't that simple. ;) Deal with it.