Fortunately we are all pretty far away from an existential war. That's the only thing keeping us alive after Oppenheimer's grand success. Even if a nation crumbles the things that replace it need to at least offer the trappings of a legitimate state if they don't wan to be immediately crushed by nuclear superpowers (assuming they themselves are a nuclear superpower or adjacent to one).

So the cutting edge isn't what's physically most effective, but what's most effective while also being within the gray and constantly shifting "acceptable" range. It's nice that we don't have to go all out, but as soon as scarcity or existential threats enter the picture things can get very ugly quickly. Best to steer clear of such things if possible. I consider chemical, biological, and weather weapons all in the same class of "you better not if you don't want to start a world war".