1) movies are edited before they are distributed; and
2) when they are distributed, they need thousands of copies from each original.
A positive to positive film copy will always be of lower fidelity than a negative + negative = positive film copy. It is inherent in the nature of the physics involved and the technology available.
Editing usually involves several copying iterations, and of course the preparation of copies for distribution adds another, so fidelity in the copying process is critical.