This is a follow up to this question regarding the difference between てある and ている.
So far I have come across two possible reasons to use てある:
てある and ている can both be used to show states, however with ている there is some ambiguity with action verbs as to whether it's the state or the action that is meant.
Would one of the uses of てある be to make clear that it's the state and not the action that is meant ? Does this discard the implication of an actor ?
Another reason for using てある would be it draws attention to the fact that there is someone who was responsible for the resulting state whereas ている is simply stating the state.
Why and when would someone want to draw attention to the actor of an action in such ?
Why is てある used in this case (top left panel):