I have often been frustrated in conversations that I have about the existence of God. In these instances it is not so much that the people I converse with are themselves frustrating, or that the conversation goes no where, but rather that they don’t take the question seriously. If I am genuinely interested in their insight to the question “Does God exist?”, I feel as though the question in itself is thought provoking enough so as to last until one person chooses to end the conversation due to an exhaust of time. Of course, this may seem all too convenient coming from a Christian who has a bit of a preoccupation with talking about God. What is the problem exactly?
To be frank, I believe the question “Does God exist?” is just as relevant as the question “What difference does it make if He does/n’t?” As William Lane Craig once put it, “[T]he question of God’s existence is so much more than merely adding another item to our inventory of things – rather it’s an issue that lies at the very center of life’s meaning. It therefore touches each of us at the core of his being” . It is for this very reason that philosopher Blaise Pascal in his Pensees had no toleration for being idle (or agnostic) on answering the question. He writes: “‘Either God is or he is not.’ But to which view shall we be inclined? . . . At the far end of this infinite distance a coin is being spun which will come down heads or tails. How will you wager?” 
Suppose however that you were to not wager. What would the implications of this be? Peter Kreeft argues that we are not observers of life, but participants : “We are like ships that need to go home, sailing past a port that has signs on it proclaiming that it is your true home and our true happiness. The ships are our own lives and the signs on the port say ‘God'” . However, the agnostic respectively says that he wishes not to pull into that port (believe) or turn away from it (disbelieve), but rather stay anchored at a reasonable distance. Why is his attitude thence unreasonable? To quote Kreeft, “Because we are moving.”
Furthermore, I believe that the existential question relating to God’s existence is demonstrably profound for our lives. Consider the following passage from Denis Diderot’s Addition to Philosophical Thoughts:
A man had been betrayed by his wife, by his children, and by his friends; some disloyal partners had ruined his fortune, and had plunged him into poverty. Pervaded with a profound hatred and contempt for the human race, he left society and took refuge in a cave. There, pressing his fists into his eyes, and contemplating a revenge proportional to his grievances, he said: “Evil people! What should I do to punish them for their injustice and to make them all as unhappy as they deserve? Ah! if it were possible to imagine it – to intoxicate them with a great fantasy to which they would attach more importance than their lives, and about which they would never be able to agree!”
Instantly, he rushed out of the cave shouting, “God! God!” Echoes without number repeated around him, “God! God!” This fearful name was carried from pole to pole, and heard everywhere with astonishment. At first men prostrated themselves, then they got up again, asked each other, argued with each other, became bitter, cursed each other, cut each other’s throats, and the fatal wish of the misanthropist was fulfilled. For such has been in the past, such will be in the future, the story at all times of a being equally important and incomprehensible. 
As philosopher Raymond Tallis once wrote: “As an atheist, I acknowledge that the idea of God is the greatest – the biggest and most terrible – idea humans have ever had. . . [N]onetheless the idea of God is the supreme marker of our existential depth” . Christian apologists have often made use of this level of reasoning so as to argue that “[i]f atheism is true, then life is really objectively meaningless, valueless, and purposeless, despite our subjective beliefs to the contrary” . Particularly, that the existence of God has huge implications for the absurdity of life if He didn’t exist  – or, that the alternative of theism calls for an important consideration of the overall conversation.
For instance, Russian novelist Fyodor Dostoevsky once wrote in his Brothers Karamazov that “If God does not exist, then all is permissible.” Jean Paul-Sartre in hisExistentialism is a Humanism confirms this, arguing that man is “condemned to be free” so as to create meaning for himself because there is no God to give it. To me, I am not at all interested in arguing this with those who are unconvinced with God’s existence – but surely, its significance can’t be ignored.
-  William Lane Craig, On Guard (David C. Cook: 2010) p. 29
-  Quoted from Reason and Responsibility, ed. Joel Feinberg and Russ Shafer-Landau (Thomson&Wadsworth: 2005) p. 115
-  Peter Kreeft, The Argument from Pascal’s Wager (Calvin.edu) p. 2 (PDF available)
-  Ibid.
-  Quoted from Raymond Tallis, In Defense of Wonder (Acumen Press: 2009) pp. 222-223
-  Ibid., p. 223
-  William Lane Craig (2010), p. 30
-  I am one who doesn’t really care so much to argue for that sort of thing. Not that I think it is wrong to do so, but that I have no interest in demonstrating the false fruit of worldviews separate from that of theism (or Christian theism for that matter) so as to show that it is in some way [morally] superior or what have you.
[*] The above image was taken from http://365blanc.blogspot.com/2012/01/somethinkfunk.html