I occasionally click a button only to change my mind mid-click. So I can move the mouse pointer off it and then let go of the button, in effect avoiding the op

I occasionally click a button only to change my mind mid-click. So I can move the mouse pointer off it and then let go of the button, in effect avoiding the operation. This ability to back out is a good for command-like events. Changing tabs not so much perhaps but probably traditionally done for consistency. X window was the odd one out in the old days that would show a context menu on mouse down. Made it feel a bit unrefined.