Well, atheists also do not believe in the Holy Fire, nor do they believe in the miracle of the Penitent Thief's cross, which, since it was installed by Saint Helena at the island of Cyprus, was hovering in the air suspended by the Holy Spirit for more than 1000 years. I bet atheists do not believe in lions digging a grave as well (lions digging a grave, what a joke
If you have no faith, you can't believe, it's easy as that. It doesn't mean that the person, who doesn't believe is a bad person (one of them actually was Saint Thomas, one of the Twelve), but it surely does mean something, which I can't formulate due to lack of spiritual vision and experience.
Any way the phenomen (lack of faith among christians) exists, and I believe we should discuss it from time to time
to help each other in one's faith issues.