Atomic warfare treated differently from Chemical and Germ warfare because of its commercial potential

The western Allies spent more on chemical and germ weapons than they ever did on atomic weapons - yet they never used them.

But surprisingly, the only thing that left and right wing historians of the decision to drop the Bomb agree upon is that part of the reason why it was dropped was the fear that Congress would wonder why a $ 2 billion war-ending weapon was never used to prevent massive American soldier casualties in any invasion of Japan.

But billions were also spent on germ and chemical warfare weapons and they too would have ended the war quickly.

So why weren't they used ?

Why was it unacceptable to kill Japanese babies by gas poisoning or germ toxin poisoning , but acceptable to kill them by boiling them alive and by radiation poisoning ?