I don't think it's a small thing where an underexposed shot on the Canon would be unsalvageable, could likely be on the Nikon. Especially considering the fact that in photography as I understand it, shooting thousands of images is worth it to get the one "money shot".
Again, you're cherry picking a single aspect of the camera and judging it for everyone by that one aspect. There are many more aspects than just that. For some people that will be enough, for other people, other aspects will be more important.
e.g. some may find the Canon more reliable (for them) in getting an in focus shot in the first place and so worrying about recovering a poorly exposed shot is rather secondary for them.