That fact seems to be lost on many atheists, who are very eager to "convert" others to their non-faith - e.g. https://en.wikipedia.org/wiki/Atheist_Bus_Campaign (I also wonder why atheists think religious people are worried and unable to enjoy their life - probably because they take the various rules of the various religions more seriously than ~99% of religious people do?).
Atheists aren't a group. It makes no sense to refer to them as a group, they don't in general meet, communicate with each other, or think that not believing in something is an important attribute of themselves that they recognise in others.
Of course for some of them, they will be more conscious of the fact that some people believe in a God, and that they don't. For instance if they grew up with religion and then left it. But that hardly describes all atheists.
Most atheists just don't believe in God in roughly the same way they don't believe in Russell's tea pot. It's not something that comes up very often.
