In my opinion, the scene is bright because if we were actually in that scene, our incredible eyeballs would be able to discern a lot of detail, and in order to

In my opinion, the scene is bright because if we were actually in that scene, our incredible eyeballs would be able to discern a lot of detail, and in order to show us all that detail, the filmmaker must make it bright. If you make it dark to make it more "realistic", you are counterintuitively making it less realistic by making it harder to see what we would be able to see if we were actually there. This balance is part of filmmaking.