Why don't some people understand lack of belief?

[Amarok]

Because people who agree with the OP want everyone to think atheists are just people who go around blissfully ignorant of a fundamental question of human existence, 

Nobody ever said were ignorant the notion of being exposed to an idea and judging that idea are two very different things . Only morons like Matthew Slick think otherwise 

"Does God exist?"

Not even close to the most fundamental question . Not even in the top ten. It important to you Wooter. 

 It is question that demands an answer and how someone answers determines whether or not he or she is an atheist,

Nope simply false 

theist, or agnostic. The possible answers are yes, no, and maybe. That's it. Everything else is just evasive puffery.

False the possible answers are 

I don't accept the proposition but don't claim with positive certainty that it is false. 
Negative agnostic atheism 

I do accept the proposition but don't claim positive certainty that it is true 
Negative agnostic theism 

I do not  accept the proposition and do claim certainty that it is false 
Positive Gnostic atheism 

I do the proposition and do claim certainty that it is true  
Positive Gnostic theism 
   
And of course i think of other variation adding Non cognitivism, Apatheism , Igtheism , Pantheism, etc 

It's not that these positions are flawed they just don't fit Wooters ideological agenda