why do we celebrate the day the transaction was made between Laszlo Hanyecz and Papa John's Pizza and yet fail to celebrate the day the idea was initiated and made public, which happens to be today May 18th?
The idea was conceived quite alright on the 18th before the 22nd May while as you have said, the transaction was made on the 22nd of May, now know this, people don't recognize intention and proclamation, instead they celebrate success, because we have intended to do a lot of things that are good enough but not of all them we achieve doing.
While until we made it completely as an achievement, it may not be celebrated, remember lots of researchers had intended to develop digital currency in the past and today we are not celebrating their intentions or plight, instead the only successful one which is bitcoin from Satoshi Nakamoto being celebrated.