Why don't Atheists realize the implications of their ideas?

If an Atheist clams there is no God there are certain implications that arise from that belief. It challenges current ideas like the nature of man, the purpose of life, how people should relate to each other, just to name a few. So why is it so many say they just refuting a claim about God? It sounds like they either aren't smart enough to understand what they are saying or are too cowardly to actually probe their own beliefs. Which one is it?