I know people that do not believe in God. To them, it is a simple question and a simple answer. If pestered they will discuss it more fully. But in general it is not a huge part of their life. Most atheists I know in real life fall into this category.
The people I have met that are more "vocal" about their atheism are few and far between. They look for ways to bring atheism into the conversation in the same way that I have been proselytized by some Christians. Both have the same feel to me.
But like I said, most atheists I know will only be more vocal about their lack of belief I God when pushed . And to me, that is understandable and is not disrespectful - it is a 2 way conversation (even though the person push religion wants a captive audience )