Aside from the considerations of reward or punishment (Heaven or Hell), just what does it do for Humans? If you are religious, you may not be able to understand this construct. But that is okay. Maybe it's not for you to stand on your own, to be vincible without a need of being fearful or so many things that religions absolve us of. Do we really need that absolution?
The religious side of this argument will typically take a side supporting religion (reasonable in a religion vs no religion argument). However, their argument will always go through a format that includes religion having always existed, or from a basis of God theory. I won't go into this here, as that isn't the point, here. I only bring this up because to argue against what is stated below, pretty much requires taking the point of view of "God is, therefore living with no God is isn't", or some sort of prevarication on that order. But that doesn't fit in this argument, although that has never stopped a deist from using it and typically doing very well with it as no one knows how to argue against it, because you are trapped within the Möbius strip ("loop") of religions argument.
So, moving along....
Belief in an outside force, a "Higher Power" as it were, gives Humans something they can't seem to find anywhere else. But actually, they can. You see, it's really just the easiest, lowest common denominator kind of thing to want and nature has solved that issue for us. It's been around forever it would seem, because it was the easiest, most obvious, and so our evolutionary history was such that it either fell easily into it, or it was designed to fit it. But it allows us to go beyond our own concerns. Naturally. Without need to turn to a superficial extreme.
We are the only creatures as far as we know that can comprehend our own demise or our own death and existence. Either that, or we are the only ones that care about it, or fear it. Perhaps some animals have the same capacity to, but just figure, "Oh, Hell, so what?" Rather than celebrating living life, most people seem to want to pray about living it or to avoid losing it. Belief in an outside force gives us license to exceed our expectations of our capabilities, to go beyond simply caring for our own survival, which is a primal instinct if ever there was one.
Add to that a fear of reprisal if we act wrong, go against strictures, break commandments, and/or, the pleasurable consideration of Just or excessive and eternal rewards after we leave this physical form, and you have the makings of what is supposed to be "amazing" behaviors. Such as heroics. A mother lifting a car to save a child, a husband saving his wife in some "super" Human way, so that it must have been undo-able, a "miracle". I love magic as much as the next guy, but sometimes we can just exceed expectations.
Many amazing things have been done and explained through religion.
But also many horrific things, I don't really think I need to make a list of them all, but the major ones come to mind easily: The Crusades, The Spanish Inquisition, Nazi concentration camps (Nazis weren't Godless Communists, they hated them, much of what they did came out of a Christian based fear and a hatred of Jews, and Blacks), Genocide, torture, Missionaries, Fascism, Neo-Nazis, and... 9/11.
And many smaller ones: sexual abuse of women and children by religious authorities, Catholic indulgences in the Middle Ages, ritual mutilations, and simply cutting people out of their religion or religious rites for abusing or breaking the rules, or sometimes and not infrequently, for very poor reasons based solely upon the religious authority's emotions or greed at that time. Or sometimes, simply sexually based as in jealousy. Even between God and an unknown object of dislike (think of Salieri in the movie, Amedeus).
Trying to stamp out natural Human functions such as sexuality, one of our most basic functions, in point of fact, what we were designed for, is defective thought, founded in theory, untenable in practice. In denying sexual expression or restrictions of Priests and Nuns from marriage, has lead to enough sexual abuse on it's own to fill a book in its various ways.
But do we need religion to achieve the depravities of Humanity? No, we can figure out how to abuse one another without an organization telling how to do it professionally and at an organizational level, which mechanizes abuse. Nor do we need religion to raise us up to the heights of what we can achieve. Because we have naturally built in, most of what religion gives us anyway. Religion is just the sugar on the crust of Life for many people. But sugar does give people diabetes or hypoglycemia when it is abused, and religion, has quite obviously supplied the same enhancements around the world and throughout history.
Religion simply institutionalizes and attempts to restrict the unrestrictable, those things we find natural, in a sad attempt to guarantee how we act. And that really doesn't work so well, especially when you consider that if you take away the all powerful aspects of it and replace it with logic and compassion, you eliminate much of the bad and enhance much of the good. Where in Christianity, Judaism, Islam (any of the desert religions (as opposed to jungle religions, some of which are worse only in different ways)) we are told that these are the rules and you don't break them. But immediately, if only in your mind, you are lean toward breaking them; albeit it, that feeling is hidden in the darker departments of your personality; yet, it is still there.
In one of the few more rational forms of philosophy, Buddhism for instance doesn't give adherents codified rules such as "you never do" this or that, but rather that you try to "walk the middle way" or try to stay on the "Path of the Middle Way". These are not absolutes but guides. They are also instructed that when you are told something that doesn't make sense, you should use your own mind and think about it and make your own decisions. Which is where the Zen thought came from, "If you see the Buddha on the Path of Life, kill him." Not something you would hear a Christian ever say about Jesus. But strangely, I would have to assume Jesus would understand it, and smile knowingly. Yet, many of his followers would be tempted to become irate or dangerous.
These two things, using critical thought and a lack of supreme "commandments", are of major importance in managing Human behavior. This is why critical thought is a major component of training with Buddhist Monks and should be a major element in all Human education above and beyond the way disciplines through which it is taught.
Often in the education of our children, we completely forget why we teach "reading, writing and arithmetic". It is to of course to teach those important things, but more so, far more so (and understand and let me repeat this), MORE SO, it is to teach critical thinking. We have far too much of a lack of critical thought around the world.
When you add in religion to a lack of critical thought; or worse, add critical thought into a damaged religious orientation, only bad seems to come of it. But if we teach children critical thought, with a good basis in philosophy without religion attached and all the dysfunctional fantasy that comes along with it, I believe we would have a far more stable society, world wide.
Still, its not just critical thought that we need to grow and properly and fully develop. Critical thought leads to creativity, which leads to thinking "outside the box". Yes, one could argue that religion is thinking outside of the box, but the trouble there is that it is not, definitely not, based on fact or critical thought processes. Just the opposite, which is why "faith" is so important. In fact, you have to discipline yourself to believe regardless of what proves to you to be incorrect in the course of things. Discipline is good, but to apply it to not being rational or evolving, is simply dangerous. As we have seen.
So now you have to ask yourself, what good does religion really do for us in the end?