I've met many agnostics who weren't aware that there are different types of atheists, including many who don't know one way or another but lean toward disbelief, which is very close to agnosticism.
The typical misunderstanding of atheism from self-described agnostics is that atheists claim to be certain that there is no God. Some atheists do that, but that's not the only kind of atheism.
Another problem with agnosticism is agnostics seem to believe that one cannot assign any probability without perfect knowledge. Yet you do it every minute of every day, in ever decision you make. We live by probabilities and beliefs (and disbeliefs). I don't see why certain concepts in life should be off limits for assignment of probabilities.