Most people I know who are atheists have some reason or life experience that has caused them to resent organized religion or they have been taught faith is incompatible with science and reason. Many of my acquaintances who are atheists have had difficult pasts where they gave up a child or have struggled with addiction or personal tragedy. I think atheism is a defense mechanism actually.
You can absolve yourself of wrongdoing if you do not have to be accountable to a higher power. Agnostics say they just don't know but atheists mostly have to take it a step further. They look hard to prove there is no God to themselves and others in order to maintain their reasoning. I find there is far more in this world to make one believe in God than not. All of nature and the rhythms of the universe point to one source of all living things. The person who came up with the Big Bang Theory was a monk, that should make a lot of people stop saying science and faith are not compatible. -BMB