You’ve gotten me thinking hard about these issues, harder than I’ve thought about them in quite a while. For that, I am thankful
It is not a question of utility but of realism. The universal belief in God is powerful evidence that it is a deep-rooted intuition which corresponds to fact. The vast majority of people reject the theory that we exist for no reason or purpose whatsoever.
The universality of religious belief is indeed evidence of a certain religiosity in human nature. Language, art, religion–and culture, generally–are all universal human phenomenon. When you say “powerful evidence,” I wonder if you are choosing your words very carefully; for, indeed, this apparent evidence is not sufficient proof, in and of itself. Ultimately, to consider this proof–as opposed to, at best, compelling circumstantial evidence–would be to succumb to the fallacy of the “consensus gentium” (the consensus theory of truth), whereby, "if the vast of human being have believed it (say, 99% of all humanity that ever lived), it is probably true. Yet mythology is a universal human creation, as well. That does not thereby prove that the content of the world’s mythologies point to something true. In fact, many of these myths more evidently stem from a need to explain things in the
here and now. Genesis explains a lot – how the world was created; what man’s place in it is; why there is suffering in the world; why people get married and have children. However, there are other creation myths, in other cultures–for example, Navaho and Aztec mythology–and they too are early attempts of human beings to explain how the natural world works, and why things happen as they do.
In addition, superstitition was a seemingly universal human phenomenon – the idea, for example, that natural disasters were caused by things that humans were doing, and that by changing our behavior vis-a-vis the gods, we could avert these natural disasters (offering an animal or a human sacrifice for example, to propitiate the gods). For the Greeks to have developed the idea that the things that happen in nature–earthquakes, hurricanes, tsunamis–happen
independently of them, was a great anomaly in early human societies; at least, it was an anomaly to believe it as calmly and as objectively as many of the Greeks did.
There is another thing that occurred to me today, as I was pondering the points that you raised – namely, that to posit the existence of a God (whether from an argument from design, or from an argument that creation needs to have a creator) does not thereby establish: A. God love you; and B. as part of God’s for you, He wants you to live eternally and to enjoy paradise.
For example – as apparent counterevidence that “God love us” (in the manner in which we conceive of love, which is concern for our happiness and well-being) one can point to the classic problem of suffering. Christianity has an explanation for why there is suffering in the world–Adam and Eve, Satan–but these are not, in and of them themselves, part and parcel of general theistic arguments for the existence of God. For the atheist or skeptic who says, “how can God love us if we are permitted to suffer; if
children are permitted to suffer,” the ultimate answer–in addition to Adam and Eve and the serpent in the Garden–is that, "God *does * love you. Even if it seems that the world that God created is indifferent–this ocean, for example, which seemingly doesn’t care whether I dip my toes in it, or drown myself; this universe in which sickness, old age, and death not only exist, but in which the first and the last (sickness and death) can strike anyone, at any time, including the very young and defenseless–even then, God still loves you immensely. This is belief in spite of apparent evidence to the contrary – indeed, faith. An argument for the existence of God–for a Creator–will not, in and of itself, establish that this God loves you and cares immensely for your well-being.
Nor will it prove–and this was startling to me–that a loving God will necessarily guarantee your immortality. Perhaps that loving God says, “I gave you this life, as a gift; I gave you the opportunity to partake in my nature; now it is someone else’s turn.” And for those who say, “but God couldn’t
love you, if you didn’t make you immortal,” I would say, “we invoke God’s sovereign will all the time, and say ‘who are we to question God’s ways?’ We say, for example, 'how can God love us in a world where, at one time, 50% of children did not survive childhood? How can God love us in a world with so much suffering? Similarly, we ask, 'how can God love us, if some of us are condemned to an eternity in hell?” (and attempts are made to invoke mankind’s free will, but the question, ‘is it fair for the exercise of one’s free will in this life to determine one’s eternal fate’ is ultimately a dead-end question; God’s ways are greater than man’s, and God’s justice is greater than we can comprehend."
Just so, if there is a God (assuming it were proved) and if God loved us (assuming that were proved), we have no proof that this loving God has given us immortality as an expression of His love for us. By most accounts, the Hebrews believed that God loved the righteous, but that this didn’t mean there was an eternity spent in Heaven with this God. Qoheleth praised God, but seemingly didn’t believe that God’s justice demanded his personal immortality. When Job complained of God’s ways, God did not tell Job, “don’t worry – as bad as this suffering was, you will be with me eternally in paradise.” This was a Christian form of consolation, and not–arguably–an historically Hebrew one.
My point there is that these arguments for the existence of God–can a clock exist without a clockmaker?–even if they were accepted as proof, do not thereby demonstrate A. God loves you and B. as an expression of that love, you will live forever. For that, you need to step beyond purely theistic arguments–does God exist or not exist–and start to invoke Revelation; specifically, Christian Revelation through the Bible and the incarnation of Jesus.
Theism is far more inspiring, meaningful and fertile than the reduction of life to a freak of nature.
This is argument for the greater usefulness–even, possibly, the necessity–for human beings to subscribe to some theistic form of belief (including, for example, the mere belief that human life is intrinsically valuable). It argues for more desirable effects through theism, than through atheism. Of course, this does not thereby prove that theism is true; merely that humans, arguably, “need” or “ought” to believe it, if they want to live inspired, meaningful, or fertile lives.
Even there, obviously, one could adduce counterexamples – of atheists who lived enviably inspired, meaningful, or fertile lives (Einstein comes to mind, as he was a great scientist and great humanitarian with a non-theistic conception of God and no conception of personal immortality). To say that Einstein was shallow would be an
ad hominem fallacy, ultimately (and a rather difficult one to prove, in my opinion

).
To say that Einstein
did believe, even if he wasn’t consciously aware that he did–or that Christ carried him and walked with him, regardless, and that the Holy Spirit breathed its life into him, and that Divine Providence showered blessings into his life–is a compelling possibility, but not ultimately proof that this was the case. If Einstein believed without being consciously aware that he believed, then the most one could establish is that–perhaps–human beings
need to believe in “something,” and that it is almost impossible for them not to believe in “something.” It doesn’t thereby establish that this “something” is real, independently of his own mind.
On a personal level, I agree with those theists who say, "I have met
very few real atheists in my life. Instead, I have met believers who are not consciously aware that they are believers, and that do not piece out the contradictions between what they
do believe in (e.g., the sanctity of life) and what they
don’t believe in (namely, a Supreme Being who loves us).
I have also marveled at how much is
possible in our lives; how many wonderful things there are, which would seem to point to blessings. And, certainly, I have marveled at the order and the mystery that something exists, at all.
But I acknowledge that these are intuitions, at best; but not proofs. I cannot explain, for example, why this God would have created a world in which half of children–if not more–did not survive childhood, until relatively recently (in the west, at least). Nor can I explain why a loving God would have created a world in which women–again, until relatively recently–died with such frequency during childbirth, such that it was a literal crapshoot, every time a woman got pregnant (thankfully, today, it is more of an unmitigated blessing). That, to me, points to an arguably *malevolent * order, an order that is put to malevolent purposes.
And, again, just because I’ve rarely–in my experience–encountered a
bona fide atheist, does not mean that our seemingly inevitable theistic beliefs, as a species, point to anything that is real independently of our own minds or constitution.