I'm an atheist for various reasons, I was raised Christian but always found that church is very boring. Later on, I realized I was gay and that many scriptures outright said my existence was wrong, (Though many of these holy texts have been edited to fit the times, Leviticus 18:22 was changed from anti-pederasty to anti-homosexuality by Emperor Constantine, if a random guy can change the holy words, how can you trust any of it?) so I pretty much refuse to believe in any of those ones. If there is an all-loving god, who knows all and is all-powerful, why is there so much suffering? And don't start on "God works in mysterious ways" or "It's free will that causes pain" I really hope that my uncle wasn't paralyzed from the neck down (From a disease that started to develop in the womb.) for almost 50 years and then died a slow death from cancer because God wanted a laugh.
Faith as a concept seems... strange to me. How can you trust something that neither you nor anyone else has seen, and the only proof is a book that was written over a period of a thousand years? Now, this is mostly my gripes with Christianity, by extension, the other Abrahamic religions, as I haven't looked in depth into anything else, but as a whole, religions drift, and if there was a sentient being behind it, wouldn't it step in so we all know how and why it was worshiped?