But you don't value every theory at equal merit do you? It's a very important distinction. A person saying that they believe that there might exist something supernatural but judges it as 99% unlikely is still by definition agnostic. But pretty far from religious and ever further away from any particular faith.
I try to avoid the use of the term "agnostic" since it really says very little. In my experience, usually people use the term because they're just trying to avoid having to think about and justify religious theories. It takes very little poking for the whole intellectual construct to come crashing down.
I'm an atheist because that's the theory that I think is most likely explanation. I don't deny the possibility of an existence of a supernatural force. But I don't consider myself agnostic. Not even almost.