It’s all about the money (as usual) - likely the economies of scale specifically. They technically can produce it almost everywhere, but it was cheaper to import it, and likely would still be even if local plants were started up.
That sounds like a problem due to the current lack of protectionism for strategic assets? I.e. it is not viable to do domestic base industry in a lot of areas.
COVID showed us that governments are quick to stop exports if they feel there is a need to.
