Why did Edith Grossman kill The Knight of the Mournful Countenance?

Haven't said a word yet about Edith Grossman's translation of Miguel de Cervantes's "Don Quixote" - it's obvious a very readable, smooth translation, she's one of the best no doubt (hasn't she done a lot of Garcia Marquez translations as well?) and she rises to the very difficult challenge of translating a comic, popular novel of 400 years ago: how do you both maintain the colloquial style but keep the novel true to its 17th-century origins and to Cervantes's style? There are no off-putting anachronisms, and she captures the many layers of tone in DQ: sometimes DQ talking in a very formal, stilted way, as if out of one of the novels that Cervantes mocks, and other times the characters, especially Sancho Panza, are very earthy, salty, and conversational. I do have a quibble, tho: I don't know the Spanish original but Grossman decides to have SP dub DQ as "The Knight of the Sorrowful Face." Maybe that's a more accurate translation, but how could anyone do better than the now-familiar moniker: The Knight of the Mournful Countenance? Sometimes translators should just leave fixed ideas alone: Are we really better served by In Search of Lost Time? I know it's a more accurate translation than Remembrance of Things Past, but I think Proust would have (might have) like the cadence and the allusion of Remembrance. What about L'Etranger? It's generally known as The Stranger. In that case, I would go with the more accurate (but less homophonic with the French) The Outsider. But what about Le rouge and le noir? Why does one recent translation decide to call it Scarlet and Black? That's ridiculous - I know French uses articles where English does not but that doesn't mean English never uses the articles. Let it stay The Red and the Black.