Well, they may be easy to make, but then you can die from they too, if you try it at home. Which is to say, biological safety systems have to be so highly reliable... And... biology labs are classified as to their levels of safety. You see, a very high level of safety is required for this work. It's very expensive to engage in. And then, once you've built the weapon, you need to store it, which requires space. In Stepnogorsk, there were huge refrigeration units, like subterranean warehouses, where the temperature was maintained around the clock at minus forty or minus fifty degrees, a very low temperature, you see. And again, then you need to deliver the weapon somehow, you need either bombs of some sort, or else missiles. Again, not cheap. You need carriers similar to those used for nuclear weapons.