Humphrey Bogart and Ingrid Bergman in "Casablanca" (Credit: Warner Bros.) When a movie is still talked about three quarters of a century after its debut, revered in the kind of hushed tones normally reserved for discussing a nation’s most precious cultural treasures, people often want to know why. In the case of “Casablanca,” that holy grail of classical Hollywood that turns 75 on Sunday, there is no easy answer. Sure, there are the iconic performances by Humphrey Bogart, Ingrid Bergman, Paul Henreid, Claude Rains and company.