I know that seems like a dumb-ass question. But hear me out.
Why should there be a real, enormously powerful entity in the world, an entity with a more real and more powerful effect on the world than anything else... and yet, for this entity and this entity only, in order to fully understand and believe in its existence, the most essential requirement is that we want to believe?
(A requirement charitably described as "the will to believe"? Uncharitably described as "wishful thinking"?)
Let's take a brief, grossly oversimplified tour through the history of religion. And I'll show you what I mean.
Once upon a time, you didn't need faith to believe in God. The existence of God, or the gods, was just obvious. Who else made all this stuff? Who else made lightning? Who else made the rain come, the sun rise and fall, the crops grow? The gods, of course. Stuff happens because someone makes it happen. If rain falls, then a rain god must have made it fall. I mean, duh.
From our perspective of the modern world today, thousands of years later, we can see the ways that people created gods out of their brains. We can see how human minds see intention and pattern, even where no intention and pattern exists. We can see how, given huge important events that people didn't understand and had no power over, they'd make up the idea of gods who they could influence with prayer and sacrifice, so they wouldn't feel out of control and totally freaked out. Etc. etc. (Daniel Dennett's Breaking the Spell is an excellent book on this subject.)
But none of this was conscious. Consciously, religion wasn't primarily based on faith. It was based on evidence, and analysis of the evidence. Not very good evidence, granted... but the best evidence available at the time.
But now, things are different.
Over the centuries and millennia, the role of evidence in religion has been diminishing. To put it mildly. We've gradually been building a coherent picture of why the world is the way it is... and supernatural beings are not part of it. The need for religion to explain the world -- and the correspondence between the known facts about the world and our religious explanations of it -- have been inexorably been shrinking.
But as the evidence for religion has been shrinking, religion itself has not dwindled. (Well, it has, but not by as much as you'd think, what with the shrinking evidence and all.) Something else has been happening instead. As the evidence for religion has been shrinking -- as God's existence has become less obvious, less of a "like, duh" conclusion -- the role of faith in supporting religion has been expanding to fill the gap.
Religious leaders and teachers, religious apologists, ordinary rank- and- file religious believers: all have increasingly stressed the importance of faith -- of believing in God because you choose to believe, because you will yourself to believe, indeed simply because you do believe. And I'm not just talking hard-core fundies, whose religion is based on the active denial of reality. Much modern progressive theology is less about, "What reasons do we have to believe in God?" than it is about, "Why is it okay to believe in God, even though we have no compelling reason to do so?"
In fact, for many religious believers, the very fact of faith -- the fact of believing in a supernatural being for which there's no real evidence -- is considered not only acceptable, but positively virtuous. Faith is often considered a finer, more pure basis for belief than trying to find evidence in the crappy old real world. And it's common for religious believers to overtly advocate the rejection of evidence if it conflicts with their belief.
If you're a believer, all that stuff may seem self-evident and sensible. Of course religion is based on faith. That's what makes it religion. I mean, duh. But if you're a non-believer -- or if you step away from your belief for a moment and look at it from the perspective of an outsider -- it suddenly seems very strange.
Why should this be so?
Why -- to return to the question I started with -- should there be a real, powerful entity in the world... for whom the single most important quality required to understand and perceive it is the desire to believe?
And why should this method of "perceiving" be not only acceptable, but superior? Why should it be better to believe in something you don't have evidence for than to believe in something you do?
There's just one major reason for atheism I would have put on the list that you left out. That's just the fact that there are so many feasible motivations (as opposed to reasons) to believe in God. After all, if you're discrediting an argument or belief, it's a nice touch to try and explain why the misguided argument or belief is widespread in the first place. And it isn't hard to identify some of these motivations. Wanting an afterlife to exist is a big one. Wanting justification for thinking of one's own group as superior is another. Wanting a sense of grand understanding of the universe (but not quite being able or ready to grasp science) is one of the more noble ones. And so forth.
Thorin is right. There are way, way too many reasons for people to want to believe in God for us to view the belief with anything other than a suspicious eye.
See, here's the thing. If you really, really want something to be true -- whether you call that "the will to believe" or wishful thinking -- that's when you have to be extra rigorous. That's when you have to make a special effort, not to argue yourself into your belief, but to try to argue yourself out of it.
You have to do this because it's been clearly demonstrated, in thousands of ways, that when we already believe something, or when we're strongly motivated to believe something, we amplify the importance of evidence that seems to support it, and filter out evidence that contradicts it. (A tendency that becomes more pronounced the more we've invested in the belief.)
And what could we be more strongly motivated to believe in than immortality? What could we be more strongly motivated to believe in than a perfect, blissful place of eternal life where we'll be reunited with everyone we've ever loved? What could we be more strongly motivated to believe in than the unreality of our permanent death, and of the permanent death of everyone we care about?
If the strongest argument you can make for your belief is faith? The fact that you really want to believe it, or that you have a strong will to believe it, or simply that you already believe it?
That's not an argument in favor of your belief.
That's a very, very strong argument against it.
The more I think about faith, the less it looks like a genuine foundation for religious belief. The more I think about faith, the more it looks like a last resort. It's the argument you make when you've run out of arguments. It's the argument you make when you know you've been beaten, but are really attached to your point of view, and really, really, really don't want to concede.
Faith doesn't look like a foundation. It looks like an ad-hoc structure hurriedly put into place, to prop up a building whose foundation is crumbling.