Early tall-building designers, fearing a fire on the 13th floor, or fearing tenants' superstitions about the rumor, decided to omit having a 13th floor listed on their elevator numbering. This practice became commonplace, and eventually found its way into American mainstream culture and building design.
Ever wonder why you've never stayed in a hotel room on the 13th floor? The answer is simple: The floor doesn't exist. It all comes down to triskaidekaphobia, or the fear of the number 13.