How do Christians live their lives that is so different from atheists?

I was brought up in a Christian home with fundamentalist parents and one of the more zealous Christian communities in my relatively atheistic country (Sweden). Despite that Christians talk a lot about God, they do not do that much to improve the world and being "the light of the world" that Jesus demanded them to be — I mean, seriously, I know Satanists (including my best friend) whose kindness supercedes that of most believers. Sure, these Christians go to churches, meet in smaller groups to discuss the Bible and their beliefs, they donate a minimal amount of their money to their churches and sometimes engage in outreach-programs. But seriously, these events are only a miniscule part of their lives and most of the time they go around living like everybody else.

This way that most Christians (I mean those who we would call fundamentalists) live is against the biblical call to even dedicate their smallest acts for the glory of God (1 Corinthians 10:31). Perhaps they are convinced that they do, but simply praying and giving thanks silently in your head regularly is hardly acting in accordance with biblical command to go out and spread the gospel, and again, to generally do good and be the "light of the world". For this reason they don't seem to take their faith that seriously and seem to do their best to enjoy their time on earth. And if life on earth is temporary and less amazing than heaven, and as long as billions of contemporary people risk eternal torment if they are not converted, why the hell do they not have the integrity to sacrifice their time and lives for the Christian cause — perhaps the idea that God doesn't exist and that this is their only life resides somewhere deep in their subconscious mind?

So, having risked being a bit inconsistent, if Christians seemingly live their lives just like everybody else, and do not differ in kindness and humanity (which appears to be near-general traits in humans overall) from the rest, how exactly do they expect that non-believers will find them any different in a positive sense?