Interesting question. I don't have the answer but it could be because it's costly to get the whole thing running. Once it's up, you want to keep it up to avoid

Interesting question. I don't have the answer but it could be because it's costly to get the whole thing running. Once it's up, you want to keep it up to avoid all sorts of problems/costs. And that's not considering how long it takes to generate said power from the plasma. Might be like an MRI machine. You could quench the magnet every other month, but at what cost and benefit?