The U.S. system is nice in that most people only even need 5 digits. The USPS reduces fees for their large customers that use all 9 digits, so they still end up

The U.S. system is nice in that most people only even need 5 digits. The USPS reduces fees for their large customers that use all 9 digits, so they still end up with the majority of their mail being very specific, while those just sending a letter to a relative can just use the 5-digit code and let the destination post office take care of re-sorting it before delivery.