On R&S, when someone asks people's religion, why do so many atheists respond 'atheist'?

Because they can't help themselves they just have to answer questions that do not pertain to them. They are entertaining themselves by mocking God and us.

If you want to get specific and particular about words then go the philosophy site, there rest of us are smart enough to know that what the answer means is "I have no religion or I'm not part of a religion etc. etc." but some people are to dumb to work that out

They say they're atheist. They don't just respond with jusy 'atheist' because atheism is not a religion etc etc.

I know you know this already

Because a blank space doesn't communicate well, and without a list, "none of the above" doesn't make sense.

It means more people are starting to realize that religion is wrong.

Because they secretly really want to believe in God, but their arrogance demands that they be the center of their universe, and this makes them jealous and resentful. Which is why, instead of doing something constructive with their time, they like to come on R&S and harrass the rest of us.

perhaps it's because some believers are unable to process the statement "i have no religion". how can they hate us properly if they can't label us? we had to make up a name for it to help them out.

How would you prefer we atheists describe ourselves in this environment? Since you object to atheists describing themselves as atheists, what would you prefer?

Because the question is asked to everybody. If it said "Religious people, what is your religion," they wouldn't answer. (Well, some of them might.)

because saying "no religion" is not the same as saying "atheism"