No, it is not a red herring. It doesn't matter that it in theory has a lot of energy remaining if there isn't any cost-efficient and safe way to extract it. And

No, it is not a red herring. It doesn't matter that it in theory has a lot of energy remaining if there isn't any cost-efficient and safe way to extract it. And the reason we aren't building them is because other forms of energy, including wind, water and sun, are cheaper.