Agnosticism is saying, in essence, "I don't know." It means the person is unsure whether or not they believe in any sort of deity. An atheist, on the other hand, by definition, is one who simply does not believe in a deity; that is, they do not hold it to be true that there is a deity. They do not deny the possibility of a higher power, or claim that they have evidence to refute that argument; rather, since no evidence has been put forth to back up the notion of a god or gods, they see that there is no reason to believe in any form of a higher power; they do not accept that statement to be true.

Agnosticism and atheism are fully compatible, though one who is both an agnostic and an atheist is more commonly referred to as a "weak atheist." Agnosticism on its own is more of a philosophy or school of thought.

In short, it's a war of semantics, and matters about as much as a small clump of dirt.
Do atheists on this forum have a need to increase their numbers by calling every agnostic the same as an atheist?

An agnostic doesn't automatically mean confused or "weak" atheist. Once a upon a time, an agnostic had a strange philosophical point of view that YOU CAN NOT KNOW. I have met these agnostics, and they do not agree with atheists anymore than they agree with theists.

Strong agnosticism (also called "hard," "closed," "strict," or "permanent agnosticism")the view that the question of the existence or nonexistence of a deity or deities and the nature of ultimate reality is unknowable by reason of our natural inability to verify any experience with anything but another subjective experience. A strong agnostic would say, "I cannot know whether a deity exists or not, and neither can you."

Understand that it its heart TRUE agnosticism isn't a confused person. It's someone saying you can not know. This is true agnosticism. Because at its heart it is a philosophy and not a belief, not only do you have agnostic atheists, but you also have . . . . . wait for it . . . AGNOSTIC THEISTS!

I think its disrespectful and the same as christian selling their bible door to door to tell every agnostic you meet that they are just weak atheists. There will always be people out there who acknowledge their own humanity, and the limitations of the human mind, and they would humble themselves to the agnostic philosophy - that maybe this is just something we will never know