Why is that? We all know that "hopeful" means "full of hope" just like "joyful" means "full of joy." And "joyfully" is the adverb form of "joyful" and means "as full of joy." "Hopefully" is the adverb form of "hopeful" so it means "as full of hope." It doesn't mean "I hope" as so many use it.
So this would be correct:
Dave hopefully asked Susan to marry him.
Now, they way most people would read that is to mean: "I hope Dave asked Susan to marry him." But what it really means is "Full of hope, Dave asked Susan to marry him."
And this is also correct:
Susan joyfully said "yes" when Dave hopefully asked her to marry him.
And that's how you can remember the correct usage of "hopefully": it's like "joyfully" except being full of joy, you're full of hope. So I hope from now on you use "hopefully" correctly.
Now don't get me started on "take" and "bring!"