Back of Hero cards?

Question towards design. Is there a reason that Hero decks do not have full size art sort of like Villans or Enviroment?

I appreciate that at least the expansion Heroes have different backs, but just curious at the reasoning behind this design choice.

It's primarily so they are easily distinguishable from villain and environment cards. You can look at them and go "oh, that's a hero."

Plus, since they are all working together they are all a single unit, so they all have similar backs to indicate as such.