Drilling, moving, refining and delivering takes time.
The reserve is a good idea, especially in the event of an EMP attack or event.
The pipelines are full. The tanks are full. The ground is full. Buying a bunch of oil and sticking it in Louisiana salt mines is not helpful. First its not that much. It won’t last us very long. Second, we can always fill it if we think we may need it in the future. Third, one bomb and its gone. Same with Cushing. Fourth, you still have to refine it. We have lots of pipelines crisscrossing the country that bring oil from fields to refineries quickly and cleanly. The Strategic reserves is like us pumping oil out of the ground and then pumping it back in so we could pump it out whenever we wish.