Why do Christians care so much about what you believe?

Being irreligious I find some arguments in Christianity utterly ridiculous. Like the question of Jesus's nature (miaphysite vs monophysite vs etc.). Why do believers care so much about such meaningless minutia? What does it change for anyone? If you want to know, just ask him personally when you die. People were persecuted as heretics for things that seem to be inconsequential to me. Why does it matter if you believe that the Holy Spirit proceeds from both the Father and the Son or just from the Father? What does it change? Why would any believer even care? I would understand if people would care what you do or say, but what difference does it make whether you believe Christ has two natures or one? I cannot think of another religion that puts so much value on doctrine... Or to make a more bold statement, why does it matter if you believe in the Trinity or you are an Arian? What does it change? Why do Christians take it so personally whether somebody believes that Jesus is god or is just god's son? I never heard Greek pagans going to war over who was truly the father of Ganymede... P.S. I don't know if this is the right place to ask but I assumed that most people here are secular and have an academic interest in Christianity...