The term “rare-earth” is a misnomer, because they are not actually scarce, but because they are only found in compounds, not as pure metals, and are difficult to isolate and purify. They are relatively plentiful in the entire Earth’s crust, but in practice they are spread thinly as trace impurities, so to obtain rare earths at usable purity requires processing enormous amounts of raw ore at great expense.

Basically the whole thing has always been a misnomer. They arent rare, nor are they found as metal naturally. But I suppose rare earth elements or metals sounds better than “abundant but hard to find rock thingies”