Churches can exist and grow so long as they meet a perceived need of its members.  In the past in the western world, the need was a fear of eternal damn*tion.  I suspect that is what is taught to many in the parts of the world where church growth is "booming".  Once that need is removed, then there need to be other reasons.  It seems that too many churches have lost their way and don't provide a true Christian community where love of God is seen through love of neighbor.  There is no reason to belong to a community that only pretends to be something, but is not.  If it is true that more people are rejecting a belief in God, I believe the fault lies squarely with the many churches who do not practice what they preach.