As sibling post noted, likely time. Existing designs have 4 decades of inertia behind them. South Korean and Japanese researchers definitely have it on their

As sibling post noted, likely time. Existing designs have 4 decades of inertia behind them. South Korean and Japanese researchers definitely have it on their radar. https://ieeexplore.ieee.org/document/9000570 https://ieeexplore.ieee.org/document/9000570