Most people I meet who say they are either Atheist or Agnostic however, seem to have a belief system that goes beyond doubing the existence of God.
They usually do not believe in any psychic abilities, deities, demons, spells, or anything "supernatural". This probably goes along with a mindset that if it can't be proven, it isn't so.
My impression, although I may be incorrect, is that it's not so much that atheism requires disbelief in these other things as it is that the sort of skepticism that leads to not believing in deities also often leads to not believing in other things that are difficult or impossible to prove. Similar mindset, but not necessarily part of the belief classification.