The best example off the top of my head is for realtime application, like a game or VR. If you setup a 100% realistic environment with Cycles then bake everything down to a texture map for your geometry, in your game or VR situation you would be able to walk/navigate around that 100% real environment for very little resource cost (no realtime shadows or lighting).
Of course that would be a static situation, meaning the illusion would fall apart if you wanted to add shadows or real lighting. But still I think it’s an effective option for very realistic lighting in a realtime application for very cheap. And of course there’s a spectrum for how much the effect is used. It could be combined with dynamic lighting if used wisely.
Anyway, hope that clarifies a bit.
