Possible contributions and harms a religion can make to society

    Christianity is obviously a massive force in the world, and has been for fifteen centuries. That is not to say anything comparative about any other religion. (There's not a "most influential" contest going on here.) First, using Christianity as an example of actual good effects and bad ones, please say: what are some possible contributions and harms a religion can make to society? Second: when Christianity itself is very clear that it is about God's mercy, not our being good, why do so many see it in moral terms: that if I do more good than bad, I'll go to heaven? Christianity quite directly teaches this will never work; only grace, undeserved favor, can save us. So why do so many people, including many Christians, think it is about "earning" or "deserving" to "go to heaven"?