Mankind needed religion as an excuse for things they couldn't possibly explain with their current knowledge. As technology developed over the past couple of centuries, more and more people realized that the stories in the Bible for instance are obviously not true (and every single person who has just a little sense realizes that - no matter how truly religious they are).
But that's not only with religion. You know about witches, stories, books about such tales, those cannot be true either! All for the favor of explaining unexplainable things.
But! For example catholic religion is not only a crap made up for this reason. Stories in the Bible help you get by, they give you a wider look at things so you can apply them in your life and make your life better.
Christianity is
supposed to be that - a help that lets you get by better in life. That's all, and I'm saying that even though I think all this religion-thing is a big bag of bullshit.
It's somewhat a way of teaching people to a better attitude, positive thinking and such, since - even though it's never been proven - THAT helps you a lot in life, and I found that out the hard way.

P.S.: this is my opinion! I am not willing to hurt anyone's feelings with it, I am not looking for an argument here - this is what I think. If you believe something different, you are free to express it, I will read it, and even if I do disagree with what you say, I won't chukkle it in your face, you are free to believe whatever you want and live by that. And I have no rights to take that or the freedom of expressing it away from you.