That's because they have a different target. If their target was other nations, they would. You don't use such armaments if your target is the domestic population. You do not want to destroy the infrastructure of your own nation. The way you suppress your own nation is by using large numbers of individuals to pick up, kill, imprison and intimidate the local population. The goal is to cow them, not kill them. You kill only those that will not be cowed and those that will inspire others to rise up. They are crafting the right tool for the job. They are building the sort of army that one needs to dominate a people that would otherwise wish to be free.