Why an area erazed is clickable ?

Hello,

why the area erazed is clickable ?

package
{
    import flash.display.BlendMode;
    import flash.display.Shape;
    import flash.display.Sprite;
    import flash.events.MouseEvent;
    
    public class Main extends Sprite
    {
        public function Main()
        {
            var sprite:Sprite = new Sprite();
            sprite.graphics.beginFill(0x000000);
            sprite.graphics.drawRect(0, 0, 200, 200);
            sprite.graphics.endFill();
            sprite.blendMode = BlendMode.LAYER;
            var shape:Shape = new Shape();
            shape.graphics.beginFill(0x000000);
            shape.graphics.drawRect(100, 100, 100, 100);
            shape.graphics.endFill();
            sprite.addChild(shape);
            shape.blendMode = BlendMode.ERASE;
            sprite.buttonMode = true;
            sprite.addEventListener(MouseEvent.CLICK, mouseClickOutsideHandler);
            this.addChild( sprite );
        }
        
        private function mouseClickOutsideHandler(event : MouseEvent) : void
        {
            trace( "click" );
        }
    }
}

Thanks