You don't have to believe, you just have to fit in. I once read somebody's theory on why atheist "churches" aren't very successful. In a real church, you have true-believers who are happy competent people with normal jobs and friends and families. They're there because of their belief, not to fill a need to belong to something. Their presence keeps the quality of the social group high so that weak or fake-believers can still participate and enjoy the benefits. If there's nothing for true-believers to believe in, then all you have is unhappy lonely people looking for company and they're not very good company for each other.

It may be hard for a religious person to say "Pretending to believe in God is more important than actually believing." so you may get the feeling that if you don't believe, it's not for you. But I think it kind of is like that. It's a useful lie that everyone silently agrees to perpetuate because it actually works better than anything truthful.