Most knives use carbon steel blades. Carbon steel contains a fine film of oil which is wiped off on first time use subjecting the blade to damage from atmospheric oxygen and moisture. With no protection, rust attacks quickly, blunting the blade edge and rendering it useless.
No-Rust stainless steel blades contain a strong chromium alloy that keeps on resisting and reformulating against rust, no matter how often they are used or in what conditions they are stored.
