It makes perfect sense to use lithium metal as an anode, as a way to minimize weight and maximize specific energy.
The problem is, it's an alkali metal, useful in a number of chemical processes -- including processes used to make meth. And so far, regulators in the US (and many other areas) have demonstrated that they'll do whatever they can to Fight the Meth Menace, no matter how much collateral damage they cause to industries, economies, and human well-being.
What kind of ridiculous regulations do you think they'll try to impose on devices that contain a multi-kilogram slab of Widely-Known Drug Precursor? Will we get cars that would have 500-mile range, but for the extra 500 pounds and two kilowatts of DEA/HSA-mandated security shielding and monitoring around the battery pack?