This is a graphicless object, meaning it acts as a Sprite object, with size, position and angle, but without appearance, so nothing gets packaged on export.
Your project may have a lot of "invisible objects" (such as colliders, camera objects, control objects). Although you may never actually use the graphic of those objects inside the game, they are still packaged on export. You end up with a rainbow of unused sprites.
This is probably a pretty insignificant optimization, but still, if you just want to have a truly graphicless object, you now have Collider.