Why does an electric knife have a nylon gear and a steel worm?

Gears are supposed to be softer than worms or pinions so they don't cause as much wear. Each tooth of a worm or pinion meshes with the teeth of the gear many more times in it's life than a tooth on the larger gear, two hard teeth meshing will wear more than a hard ans soft teeth. Having a steel gear would cause the worm to wear out too fast. Ideally the worm wheel should be phosphor bronze but bronze is expensive and plastic is cheap.

Any time if 18 but would need the money

True is the answer. hthhth