IMO it's mainly because we only tend to make a big deal when certain anniversaries arise--like the 50th, 60th and so on. 63 isn't that type of number, unfortunately. In 12 years, I guarantee you that the 75th anniversary of it will get huge attention.
June 4th is a much more significant date in WW 2 history anyway. How many people can tell me what the significance of that date is without Googling it? Here's a hint--it's the day that the tide of the war in the Pacific turned due to the bravery of a handful of outnumbered and undergunned aviators, flying obsolete aircraft against the cream of the Japanese military, against overwhelming odds. It's right up there with Trafalgar in the annals of Naval history. No one ever marks that date, or remembers the brave men who died on that date. I'll bet you right now that June 4, 2017 passes with hardly a mention
