Most people do say they don't believe in God but that's not true, everyone has a God, whether a dead god or a living God, even the dictionary defines God to be anything we make Supreme, being our house, money, car, job, husband, wise, etc.
Until you discover a God, live purpose on Earth become useless, cos your object of Supremacy is your source of happiness or sadness, and everyone knows that, if what you are doing is not clean its the opposite which is sin(not perfect) but we justify sin with our selfishness interest and call the unclean '' new style of life''
Even if we admit that we have nothing right and wrong it tells us that there's someone who decides that which is God.
Heaven is real whether you believe it or not, just tell the first time you were set free from all the things you were enslaved to do(alcohol, smoke, rape, cheat, kill, abuse, fights, arguments, etc) you can't do anything about it until a man from His house(Heaven) invades on your behalf, he set his own(children) free, all you need to do is to accept him as your lord and personal savior.
CONCLUSION: IF YOU BELIEVE THERE IS SIN,IT MEANS THAT THERE'S SOMEONE WHO DECIDES THAT WHO IS GOD AND IF YOU BELIEVE THERES GOD, IT MEAGAN YOU BELIEVE IN. HEAVEN HABITAT.