Well, there is actually a reasonable reason. Typically you'd want the government to hold people accountable so you could have the thin veneer of operating by the rules of warfare and not committing war crimes. That's usually been a popular strategy of the US for when someone goes a little too far (or gets caught).

As far as I can tell Israel doesn't particularly care for even looking like it's trying to behave responsibly. I don't think they've held anyone responsible for even some of the most obvious war crimes we have evidence of being committed.