There are some who once believed in, and trusted God, but walked away from God because they feel he let them down.
Some don’t believe in God because they believe they’re not worthy of God’s love, or that God couldn’t possibly love them.
Others have never heard of God, so have never made a conscious choice to turn away from or ignore God.
Whatever the reason why some non-believers don’t believe in God, those of who are Christians are the ones who have a huge responsibility to show them Christ. No matter how much non-believers hear about God, his teachings and his promises, if they can’t see Christ in us through the way we live our lives, how can we expect them to believe what the bible says?
Live the bible each day, then others will see Christ in through us.