You can discuss religion without participating in one. It has sociological, historical, psychological, logical and philosophical aspects. Scientists are nerds, nerds have large bodies of knowledge in certain areas, whether or not its within their formal discipline.
Atheism correlates highly with science because the tools of science are critical thinking and logic. Finely honed critical thinking skills and religion go together like Jack the Ripper and industrial chainsaws. Religion attracts people through transcendentalism, spirituality, faith and all that other unspeakable crap. Scientifically, there is no basis for such things.
You might also speculate on the reverse causal link: Atheists don't believe in all the usual goddidit/religiousy/spirit explanations for questions that provoke their curiosity. Since they think religious sources have no special validity, and are consequently, a piss poor source of knowledge, they are driven to pursue Decent Answers™ and enter the sciences.
Also, because there is such a poor logical case for the existence of God/big giant boats/ magic angels etc. atheists almost always win any debates regarding these topics. Winning is fun.