The real question is why it took more than half a century for the government of Japan to apologize for the Rape of Nanking.
Or the dozens of other horrible things they did during World War II and the decades leading up to it. I have nothing against the Japanese people, but their government and a small sector of Japanese society are seriously f***ed up and totally unapologetic about the whole affair.
And while Pearl Harbor was a legitimate military target, they still launched an unprovoked attack on the United States in order to continue their genocidal war in East Asia. Japan was unequivocally one of the bad guys during the war.