Of course the photographic negative exists in nature. You can hold it in your hand. It occupies space and time. It was present in front of the subject when the scene it depicts was recorded onto it. The scene depicted on the negative is the abstraction.
The digital image does not exist in nature. The imaging abstraction has been carried to the point where the very physicality of the medium itself has been removed. The image exists only as an idea. A non-physical logical pattern. A pure abstraction.
It's sort of like the number '8' is only an idea. You cannot hold an '8' in your hands. Can't buy one at the store. It is a concept. Although its logical value will almost certainly be found somewhere as part of the representation of every digital image, it was itself not physically present at the point of exposure. It couldn't have been. It's not a thing. It's a pure abstraction.
Both approaches are capable of recording an image abstraction which represents the scene before the lens. But one recording is itself a physical thing, while the other is not. While a paper map may abstract the territory it depicts, the map itself is not an abstraction.
Some of us prefer to work with physical things. Within the context of a photograph, that distinction matters to us. Others don't care as much.