Rare earths are not actually all that rare, they're just present in very low concentrations and require tons of processing with nasty chemicals to extract. Those startups etc aren't sitting around twiddling their thumbs for kicks, they're mostly mired in bureaucratic approvals and/or lack of finances due to a very justified fear of those approvals. Throw in the wild price fluctuations and it's much easier to just buy everything from China, which already has everything in place.