Of course you don't become an atheist if you really believe in God. But if you logically have come to the conclusion that there is no god, should you still lie to yourself? I don't see what good it will do. On the contrary, a false belief in gods has several disadvantages. As an atheist:
1. You don't have to believe the preachers on funerals when they tell you that your loved ones where sinful. (I found it extremely bothersome on my grandfather's funeral that the preacher talked about sin all the time; and I'm glad I could reject that as religious superstition. Unfortunately I had to listen to the bullshit though.)
2. There is no one watching you when you masturbate, have sex, go to the bathroom or do anything else private. If I believed in such a god, I would certainly become totally paranoid.
3. You don't run the risk of being punished eternally for your opinions. (i.e. you are not sent to hell for not believing the bible)
4. You won't be as easily fooled to give away all your money to impostors
5. There are no evil creatures or devils to fear (except for religious fundamentalists. Some of them are really dangerous, such as people that blow up abortion clinics, kill doctors or issue death penalties on authors)
6. You don't have to waste your time reading ancient myths to decide how to live.