If the factory isn't used you have no idea if it will work. Did mice eat the wires? Machines rust? Did we discover the something is hazardous and we wouldn't use it? Is the thing obsolete and we wouldn't want it anymore? Do we have people who know how to run the factory? This is one reason why the army has thousands of tanks they don't want (the more cynics say is is a jobs program that congress forces on the army - you decide which view you want to take, but both are valid)