The two-letter state abbreviations were implemented in 1963 to make room for the roll out of the Zip Code. Until that time, the Post Office Department (that's right the USPS wasn't established until the big reorganization of 1970) preferred that the state names be written out in full. It was you people who liked to abbreviate everything, so they did come up with preferred abbreviations if you have to do it.
Sorry, I'm not a comedian, but I am a postal worker.