Why blockbusters film under fake titles

When multi-million dollar film productions scout locations in crowded cities, they never use their real titles. Massive science fiction and superhero franchises use incredibly boring fake working titles to deter obsessive fans and paparazzi from swarming the sets. A high-budget superhero movie might discreetly shoot on city streets under the guise of an indie film called 'Blue Harvest' or 'Frostbite'.