There are 'atheists' who subscribe to some sort of divinity or 'spirit' but they're not atheists in the true sense. Atheism isn't a religion. There isn't a book we all read or anything, it's just having a rational debate equatable to "Everyone believes in Santa. Never seen him and the only people who told me about him were my parents and friends, and Christmas songs, but they haven't seen him and there's nothing really out there."
That doesn't make an anti-Santaist, just someone who doesn't tell children there's a dude in red with an unhealthy addiction to stale cookies and dairy that's been out too long.
There are humanist atheists, Buddhist atheists, Jewish atheists, Taoist atheists and Christian atheists, some of them "strong" "ashes-to-ashes-dust-to-dust" atheists who find value in the specific teachings of their belief systems but deny any supernatural influence or existence.
The misconception that most people have about atheists is that there is a common belief system.
A number of atheists are really anti-Christian, anti-clerical or anti-theists, not true atheists, so they're fighting against Christianity specifically (other faiths have their detractors but Christianity seems to really bring it out).
As a 'strong' or 'hard' atheist, I lack an external belief system based around any theistic argument. I don't believe in anything, not "I do believe in nothing." It's a semantic argument, but one with weight.
Most atheists subscribe to basic conceit that "I don't believe there is any sort of spirit, God or life force" which is different than "I believe there is no sort of spirit, God or life force."
I see all faiths the same way we look back on extinct religions. We can derive moral stories from Zoroaster and the myths of Hercules, Gilgamesh and Mithras, but there's no need to slit a bull's throat on the winter solstice for prosperity for next year. Good stories, but so is "Lolita" and "Fear and Loathing in Las Vegas."
The root of the issue beyond it all is the theocentric argument of "... since there is no evidence that can prove the [nonexistence] of a god." That's an agnostic cop-out based around a theistic belief system.
It's not up to us atheists to disprove god. There isn't one cause there isn't.
There isn't a monster under your bed either because there just isn't.
It's up to agnostics to argue that "there might be one but we can't prove it either way," or theists to prove, "there is a god, you can't see it, but trust us."
When this question is reframed, it can be pushed to the point of absurdity, "So god watches us? Like all the time? From where? And he knows all the things we do? And so he sees the times we 'sin' and the rationale we formulate, yet still act? Doesn't that seem counter-intuitive? Considering he knows we feel a little bad?" Etc.
If you like religion, great. Pray, hope, indulge in ritual. Just don't be a jerk.
If you can see the inherent human-centric arrogance in believing that an all-powerful deity has the time or interest in weighing the souls of people based on they think or feel then maybe you'll cross over into rational atheism. But at least explore all the options in your own head. When we die, we'll know what the real deal is.
Of course, as an atheist, it'll be slow fade, bright flash as neurons fire for the last time, then nothing.
Nirvana.