I've often considered what attracts different people to religion and what purposes religion has served in society. Recently, I've been thinking of the converse: what makes people reject religion and the different reasons why people are either atheists or agnostics.
I think there are several reasons, often depending on each particular person's personality and outlook on life. A few types immediately came to mind:
First, are the scientific types, who reject religion because there is no proof as to its claims, because it defies reason and logic.
Second, are the "pull yourself up by your own boostraps" types, who view religion as a crutch and a haven for the weak who refuse to stand on their own two feet.
Third, are the hedonists and non-conformists who view religion as a series of lists with arbitrary and outmoded rules about moral behavior that are negative in nature. To them, religion can be summed up as "Don't Do This" and see religion as a way to suck all the joy out of life.
These are the three types that most readily come to mind. Personally, as an agnostic, I'm a mixture of reasons one and three. I'm not so much the second reason, because I have no problem with whatever gets people through the night, as it doesn't affect my freedom to do differently.Feel free to chime in with more types of skeptics and unbelievers.