Because if you don't talk about war crimes, and you don't admit to war crimes, and no one pays any attention to your war crimes ... what war crimes?
"Unlike Germany, Japan never came to terms in any way with its wartime history. The Japanese are fed on a diet of official history and pop culture history which makes them out to be the victims of American aggression. This history typically starts with American planes suddenly bombing Japan for no reason and then concludes with Hiroshima and Nagasaki."
Link follows. Warning: this is a very disturbing article. "Japan Still in Deep Denial" here