Because there is no positive case for religion. What you deem as "positive cases" for religion, are actually just acts of goodness by people who care for other people. That has nothing to do with religion.
The fact that you have to attribute acts of goodness to religion, means that you yourself have such a negative view of humanity that you think the only thing that keeps us going and being "good" is your OBG.
Dogs do good things for other dogs. They don't go around yapping about Puppy Claws being the reason they do what they do and how other dogs should believe in it... They just do it because it is natural. Helps them maintain their species, their family, and themselves.
You, on the other hand, have this belief that without God or religion, we would all kill everyone because we don't have direction or a common goal or a sense of morality.
My argument, is that religion is the one killing everyone. Sane people like most of us here realize that, and shun religion for the evil that it is.
Religion has never caused any good. It has instead attributed to itself "good" things that humans normally do, as the reasons they do it. But that is false, and why you are brainwashed.
Religions would decimate a population and steal all their riches, and take the people that survive as slaves, and use that money and manpower to build holy monuments and cathedrals for their followers to visit, but that is actually NOT a "good" thing as you seem to believe! It is a very BAD thing...
So tell me something negative religion has done, if you're such an objective thinker...