Gimmick...maybe, but they use it and it's marketing genius for their type of business. I mean, it tells people it's always a time to celebrate and that goes hand in hand with all of the other aspects that make the bubble magical for most. People who are encouraged to celebrate "something" are more likely to spend more $...often A LOT more $. Maybe you book a few extra TS meals and indulge more with what you order, maybe you buy a few more special treats in the shops, maybe you book a longer trip at a higher level room grade or resort because it's now a special trip, maybe you add on cakes and in room celebrations, maybe you book special things like dessert parties or tours, etc. Either way, if you're encouraged to celebrate, you likely put more $ in their pockets. And while some do it just because they can and it's encouraged, enough people have decent enough reasons to do it that it would be insanity for the company to argue or police the practice. So instead, they promote it because it's probably a cash cow for them.