I don't listen to country music. I don't like country music. I don't believe country music is worth listening to. So does this make me an "acountrymusicist"?
That is, someone who holds to a belief that country music sucks. No, I just don't like it.
I pay very little attention to it, noticing this musical genre only when it is is foisted unwillingly on me by a radio station, TV show, or store.
Likewise, I don't consider myself an "asoccerfan." I just am not much interested in soccer. Same goes for religion. So why should I be called an "atheist" if I don't believe in theism?
Mostly because theism is so widespread. Almost everybody in the world believes in some form of supernatural entity, whether this "God" is personal or impersonal.
Christianity, a theistic religion, and atheism simply are not on a level. Christianity is a thing. Atheism is an absence of a kind of thing, namely belief in God(s).
People are labeled "atheists" only as a sad consequence of the fact that until very recently, belief in God was taken to be essentially expected, making atheists relatively rare and obvious in that they buck a widespread norm.
By analogy, I suppose, if we had a culture in which nearly everyone from birth is taught to play golf as a social and cultural imperative, we might have a word for those rare individuals who end up not playing golf. As it stands, we have no such word, and we need no such word.
Such a word may not even be needed. For example, by what term do we call people who do not watch television? Television non-viewers? Atelevisionists? I am one of them, so I know they exist, and I know we're quite rare and bucking a societal norm. The same is true of "atheism," at least in principle.
Now, as an aside, I should illustrate how this misconception is getting legs under it because that's its own problem. I'm noticing more and more that people are misidentifying atheism as a thing, and it is not just those religious believers who seem unable to conceive of a lack of religious belief.
Instead, people who self-identify as atheists are frequently confusing this matter for themselves too. This confusion gives arguments like Evans' an undeserved veneer of potency, so I would implore people to try to be more cautious in this regard.
Indeed, I am more and more often hearing people talk about "atheism" as if it is a thing one can join. Furthermore, they talk about it as if it is something that can be done well or poorly!
Perhaps, as someone who has played a round of golf only once in his life, this is a bit like how I've very nearly perfected my not-playing-golf game? Maybe it's like how picking up a good book helps improve my television non-viewing?
...To close this aside, then, here is a warning to people who do not believe in Gods: by identifying "atheism" as a thing that can be joined, can be done, or can be gotten better at, and by founding "atheist communities," those involved are providing credence to the notion that atheism is a thing--a thing rather like Christianity, in fact. Take heed of this.