I also started thinking about it reading the reviews, and the main cases to me are:
- checking something before commiting an action: for instance reread the product name before pushing the purchase button. The pointer is already on the button, I keep it there while checking the order, so I just need to click.
- focus switch: pushing another window to the forefront doesn't need a super accurate click. I assume most people eye ball it like me and will click on a emptyish part of the window from the corner of their eye. Same for moving the focus away.
- scroll and type like situation: mostly when using a document on the side while taking notes. My eyes and focus will be primarily on one side (with quick glances on the other), while the mouse/trackpad movement will be on another.
I think we'll discover a lot more instances of this.