It's fun. Lucas by no means believed that his salutation greeting was a pun. So someone added the holiday, probably, to poke fun at the strict notion of a Star Wars cannon. That is debating the pun's relevance by certifiable star wars fans was a contrariety. If the took the debate seriously they undermined the own credibility. Hence the accepted humorous nature of involvement in the celebration. The irony of which is that it's not really celebrated so much as spoken of being celebrated. Thus adding more absurdity to participating.
Caption this Meme
