Yes, 2D assets can be reused, once you have a 3D asset, it can be used with a lot more spectacle. Of nothing else, when you're animating a change of visual angle, it's a whole lot more convincing and easier (animate some positions) vs the 2D alternative of having to animate or rotoscoped each of the pixels and frames for that gun motion.

And spectacle was one of the biggest sellers of games.