Its effects are still more isolated. You can get a little closer with shit like dioxins, but youre confusing momentary emotionally impacting easily comprehensible spectacle with total harm, which can keep happening and have nth order effects so many degrees out. Populations and centuries. Chemical weapons cannot turn you and your grandchildren to erasing evidence you ever existed even when they turn your bones to acid soup and dissolve you from the inside.

Dying of horrible neurotoxin happens to a person, its direct. Its easy to empathize with, easy to attribute, easy to understand, easy to be afraid of. Its an attack of spectacle. If it was more devastating than blowing people up, more militaries would use it.