In my experience, most people who don't believe in God are either mad at Him or disappointed in Him, or think they are too smart to believe in Him, usually relative to their inability to perceive Him.
Careful, it's easy to be unfair when ascribing hidden motives to those who disagree with you.
In my case, I don’t believe in gods because I don’t trust myself to believe in things that I can’t verify. In an abstract sense, you can look at all the people around the world who believe in things out of faith and see that most of them are wrong. Obviously people can’t be trusted to place their faith in the right thing. Most believers consider themselves to be exceptions to the general rule.
On a less abstract level, I don’t believe in the supernatural because when I did so it put me into suspect company. There was a time in my adult life when I believed in God, the soul, the afterlife, and what have you. But I found that other people who believed in such things also believed in things I didn’t believe in, such as astrology or Hell. I would read a book about spirituality that mostly made sense, but then the author would inject some crazy beliefs. It became clear that there was no way to differentiate the unverifiable beliefs that I took to heart from those that, to me, were nonsense. No way to do so, that is, without ascribing to myself superior spiritual discernment. So for a while I understood myself to have superior spiritual discernment, but that was such a patently self-serving delusion that I couldn’t maintain it.
It was humbling to give up the idea that I had discerned spiritual truths lost on the majority of humanity, and that my eternal soul was part of a cosmic plan. But that’s what the scientific world view is about: humility. Scientists know that people can’t be trusted to intuit the truth, so they hold themselves to standards of verifiability.
While human belief systems are a special interest of mine, I recognize that the important thing is how we treat other people. Don’t mistake my fascination with the various things that people believe for the idea that doctrine makes much difference. It’s precisely the fecklessness of doctrine that allows human beliefs to take such extravagant and amusing forms.