I would guess it is because it is much simpler to do, like you can visually set the size and angle, also the values of each variables, it also forces you to set it, since it takes this instance you create as a reference (even in the editor itself, have only one instance of a sprite, change it's size, then add another one in the layout view: it is the same).
Also I would guess the object type define more the reference of the identity, more than the actual settings of it.
Anyway, I think it would be more trouble to have to set it without a visual representation anyway.