The year 1953 was marked, in science fiction, by the following events.
[1] The awards presented that year were initially conceived as a one-off event, though the organizers hoped that subsequent conventions would also present them.
[2] At the time, Worldcons were completely run by their respective committees as independent events and had no oversight between years.
Thus there was no mandate for any future conventions to repeat the awards, and no set rules for how to do so.
[4] The nickname was accepted as an official alternative name in 1958, and since the 1992 awards the nickname has been adopted as the official name of the award.