Henri Langlois spoke about the snobbery of curation. As a young man, he was offered what was likely the only surviving copy of Theda Bara’s SALOME.
He turned it down— why waste resources on vamp trash?— and the film is now lost.
Later, he realized what an ass he had been.
For another, even bad movies have artistic and cultural value. Hell, even mediocre ones do. They may not hit when they arrive but could provide important insights about the time in which they were released, inspire other art that makes a big impact, or improve with age.