Presidential honors were actions done as a courtesy for visiting presidents.
In 2269, in response to the apparent visit of former President of the United States Abraham Lincoln, James T. Kirk told security to be prepared to give full presidential honors to him. When Montgomery Scott called it nonsense, Dickerson explained to him why these honors were being given, which caused Scott to doubt his sanity. Kirk later explained that he didn't believe it was actually Lincoln coming aboard, but that they were doing it just to be safe. (TOS: "The Savage Curtain")