Ahhh. Important distinction.

In that case it is likely just a cost and practicality thing. Copper alloys are significantly more expensive than stainless steels or plastics. They’re a little harder to form and shape as well due to their cold work hardening properties (the more you bend it, the harder it gets, until it breaks; stainless is more ductile in this regard).

It would be pretty, but I guess manufacturers have likely not determined an economic benefit to making a higher end, more expensive, harder to manufacture razor body out of these metals.