I would assume same reason why in the nuclear warfare logic, it’s a threat to build anti-missile tech. If you start building nuclear shelters and also have capa

I would assume same reason why in the nuclear warfare logic, it’s a threat to build anti-missile tech. If you start building nuclear shelters and also have capability for first strike, your adversaries are within their rights to think you are escalating, since you are increasing your population’s resiliency to a second strike (hence making it less costly for you to strike first).