This is such a common question; I think this is how it went.. people believe because they're scared that if they don't, they'll go to hell. But in reality, they're not sure which is a sin too. Nobody is really sure but everybody 'believes' because of the term, 'better to be safe than sorry.' Even then, if there really is a God, he would obviously know our faith on the whole question, 'Is he real?'
Some people say they believe because - well if you don't, then you're an outcast in some old fashioned towns. I know, in one town.. you cannot get away with saying God Isn't Real. It could easily bring your social status down by not going to Church, etc. Obviously religion is one of the biggest things in the world. I think the question shouldn't be.. How come so many people still believe in God? But - Do people really believe in God or are they scared shitless of admitting that they're unsure?
So, some people may not believe but say so because of their family, social status, whether or not he is real or not.. um. And some might whole heartedly believe because of an experience and a 'white light', my whole opinion on it is really.. I believe that it was just a way to gain power. Oh, not to mention people were scared into believing it because of the ages of when people would get set on fire because they didn't believe, 'witches', so those people went in with the whole 'faith', and sent it down to their grandchild out of fright for their lives.
So really, the question is, 'Do people really believe' rather than 'Why do they believe?'
-Doll