Just because you find it impractical doesn't mean it is impractical. If your definition of 'god' is an omnipotent creator god, then every polytheist I've ever known is an atheist. You need to define the parameters. Are fairies gods? Then I am a theist. Are fairies not gods? Then I am an atheist. But, then you are telling Celtic pagans that their gods are not gods.
It is impractical. Not in terms of having a one on one or small group discussion. But when creating labels and using them to categorize a broad group of people it is very impractical. So I should not consider myself an atheist in general as I have not examined every single god concept in existence and determined whether I believe them all individually?
Actually, you can. If you couldn't, there would be no such thing as cognitive dissonance. IE: excessive mental stress and discomfort experienced by an individual who holds two or more contradictory beliefs, ideas, or values at the same time [A Theory of Cognitive Dissonance, L. Festinger, Stanford University Press, 1957.]
In other words, humans are perfectly able to hold contradictory beliefs, it is only when the stress reaches an excessive level that cognitive dissonance enters into play.
For example, many Christians believe in a god who is omnibenevolent and yet jealous. These qualities are contradictory, but they still hold those beliefs.
I will have to look more into cognitive dissonance when I am not at work, I am responding quickly when I have some downtime. From the example you gave, it is exactly what I said. They have two separate beliefs and two parts of it overlap and contradict, but they aren't holding the position I believe in this thing and disbelieve in the same exact thing at the very same time.
but you are stating that it is inherently an atheistic one. IE: if I say I don't know, I must therefore believe the cat is dead. By saying agnosticism must be a negative response, IE a disbelief, you are saying there is no neutral position, no one who can hold a fifty-fifty position.
The difference is that theism is a positive assertion that a god does exist, therefor Schrodinger's cat is not a very accurate analogy. Theism is essentially "the cat is dead" and atheism is simply the rejection of that claim until the box is opened and we can actually determine the state of the cat. That's why it is the default. The person making the positive claim holds the burden of proof, not the other way around.
Also, theism and deism require you to be convinced either by being raised, taught, studying the bible or however else you may come to this conclusion but you are not born a theist. When you are born, you have no belief in a deity, therefor your default, natural human position from time of birth is atheism.
Actually, it is perfectly possible to hold the Copenhagen theorem of quantum mechanics, which is to believe that there both is and is not something in her hand, until you observe it, at which point it when observation performed the wave function collapses into one of the two states. [Quantum physics & observed reality: a critical interpretation of quantum mechanics, Hermann Wimmel, 1992].
This I will also have to look into when I have more time. Sorry I cannot be more thorough at this very moment.
The reason "I don't know" equals atheism, is because if someone makes a positive claim, lets say "the cat is dead" and you say "Sorry, I just don't know yet" do you believe them? the answer is no. You don't necessarily disbelieve but you are not a theist. If you are not a theist, you are an atheist because you either believe in a god or you don't. Most likely a weak atheist. You aren't making the opposite assertion that a god absolutely does not exist, but you are rejecting their claim of theism.