Someone once said: "An atheist can't find God for the same reason a
thief can't find a policeman". I think that pretty well describes the
primary cause for atheism. Of course, spiritual ignorance would be a
close second.
Ditto what physics said. Why don't you tell your god next time you pray to him to come pay us atheists a visit? He should know right where we're at, right? That should end all doubt instantly. No more theives--er, atheists!
Also, I would contend that you are the spiritually ignorant one. You can not imagine a worldview outside of that painted by your narrow religion, and you are supremely and grossly ignorant with regards to the thinking, background, and motivations of atheists. Many atheists I know are quite spiritual. Spiritual is a state of mind, and requires no belief in the supernatural. One does not need a creator god to feel awe when gazing at the heavens.