Why does the Blu-ray of Star Wars: A New Hope still have the "boxes"

I noticed this acutely in The Empire Strikes Back. It's a problem with the film-to-digital transfer, where the transfer engineer known as the colorist brightened up shots that were meant to be dark, revealing flaws in ILM's rotoscoping, painting out blue-screen edge masks, that were never meant to be seen and wouldn't have been seen on film in a cinema. Correctly adjusting your TV for black level using the Pluge test pattern in a test disc like Digital Video Essentials helps.