Much as the US has "libertarians" who are not anarchists, no, really, they're not, honest[1]. You also have agnostics, because the direct threat to God's Own Country posed by athesists can make it uncomfortable at best to proclaim yourself an atheist.

Plues there's the native pedantry amongst scientists and engineers that makes the certainty of atheism uncomfortable for some of us.

[1] actually, libertarians are not anarchists, any more than muslims are jews. Their underlying philosophy derives from anarchism, but they've swerved back to become militant statists which is truly bizarre from an anarchist point of view. But in some ways the parallel holds - it can be dangerous to say you're an anarchist/atheist, so there's a softer term in common use that basically says "I'm an X but I don't want to argue about it".

And Brad, your question is case sensitive. Pedantic!