It makes perfect sense if you know how the courts work. The ICJ isn't a regular court, it handles cases between nations, so it cannot (by definition) be compared to a regular national court of nation country, it's a fallacy to do so.
A victim nation is not a person, if a person in the nation dies, the nation will still exist. Iraq, if it wanted to, can file a case against the US and the UK, hell, a regular Iraqi could, but most people don't know this, so nothing like this happens.
I suggest you actually read about the courts before passing judgement on them, as they've been quite effective, even if they have their flaws.