It's also way easier to have "good colors" (in a color theoretical sense) this way, and achieve a coherent and consistent look throughout the movie. It's thus one of the best ways to keep budget down, as it will hide a lot of issues you'd have while filming, while generally requiring less work. I believe it to be an important factor since full 3D movies have excellent color comps --see for instance Nathan Fowkes' works. (as an side, in the opposite direction, I remember Kung-fu Panda having pretty good colours, yet I found it a bit tiring to watch.)