I think I'm with Bart, mostly, on this. While I get the push back to the commercialization of these things, and the formality, and the false creation of the expectation, I do think it's probably not the worst thing in the world to be kinder to people in our lives.
(Funny story, except if you're one of the principals: a friend of mine has been forced to address a staffing issue in her organization, and finally came to the unfortunate resolution that she had to let someone go. She made the plans to replace them, etc. and with flex time working had to coordinate when everyone was in the office to actually pull the trigger. She gets in to the office that day and someone says "Happy Admins Day!" She's like "wait, what? I'm letting my admin person go on Administrative Assistant's Day?!?!?" I told her, though, that one made up "holiday" doesn't change the performance over the last three, four years and doesn't change the decision. If nothing else, when we're old (well, older) and gray (well, grayer) you'll have a great story to tell.)