Japan HAS officially apologised for those, more than once. And paid compensation. Despite a handful of idiot Japanese politicians throwing spanners into the works.
The trouble is, the apologies can never be good enough, and indeed Asian countries don't WANT Japan to apologise - they make it as diplomatically/politically difficult as they can, to prevent it.
Because it's such a handy go-to... to wheel out when things are going badly at home, and the politicians want to look all strong and nationalistic, and divert attention from domestic affairs.
More info --> here. Buy the book if it's something that interests you.