Primitive man's Ignorance. Emotionally damaged people that need emotional comfort no matter how ridiculous their solution is. Control. To stroke the wishful thoughts of people. To lessen people's fear. Many, many more........
I believe that we don't absolutely need religion, as far too many religions have been perverted into cults. However, we do need a relationship with the real God, which is certainly not the same thing.
We need religion for salvation. If you have no faith you have no hope and after death all you're going to end up with (if you're lucky) is death but most religions agree you'll end up with torture in hell. The Bible explains the need further.
People can't quit making the mistake of buying into them. They are addicted to the culture of conflict and agree that if we can think of a good reason to kill, oppress or subjugate others that we should do that. The proof is in the pudding.
Religion must be true because most things go AWAY in a few years and are forgotten. But religion does NOT go away. It is here to stay. In christianity .. It gives us knowledge of who made us.. Where.. When and why. It tells us how to live a good life & to love God and people. Thats the formula for happiness. It is mankind that has caused problems by not following the guidelines.
Many religions are a trick of Satan. God, the Creator of the universe, desiring a relationship with humanity has Satan as his enemy. Since Satan cannot get rid of God, he complicates our minds with various religious beliefs which have drawn a vast multitude away from God. The Bible explains religion like this; James 1:27 KJV Pure religion and undefiled before God and the Father is this, To visit the fatherless and widows in their affliction, and to keep himself unspotted from the world.
To explain what was happening in the sky. To control people in a group. To explain what happens after death. To identify 'us' vs. 'others'. To form community with rules. To get money from less educated people to support the leaders.
I think religions started off as explanations of why things happened. These explanations were formed into doctrines and became known as religion. The explanations that couldn't fit anywhere are now called superstitions.
Science provided an alternative explanation to why things happen and has, for the most part, replaced religion. But because religion alleges to explain more then science does, it hasn't been eradicated by science.
I think we have to look at why there is religion, meaning any and all. There has always been a need for explanations to larger questions and ancient peoples did the best they could. Too often however, these 'answers' became a cause to indoctrinate simple folk into a fold of control. Often cradle to grave. Few if any religions update their message to absorb what man has learned in the millennia since the ancients scrawled their initial hypotheses. So much of what supported ancient faiths was wallpapered over by subsequent religions to the point that now precious little has any basis in fact. It's about what people allow themselves to believe, and for many the simple outweighs the logical. Religion arose in the absence of better knowledge, and exists today in spite of it.
For comfort. We want to believe there is something after death, that we have not really lost our loved ones. To explain how we came to be, to explain our nature and the nature of other creatures around us.