Why not? If the airline has a policy that allows them to fly, why wouldn't they? It's not the people with allergies asking the flight not to serve other people peanuts, it's the airline itself deciding to do that.

Besides if someone has a contact allergy to nuts, I can't think of a place more likely for it to happen than a plane. One patch of turbulence, and your seat neighbor's peanuts go all over you.