Thank goodness F.F.C. did not film "Apocalypse Now" at Malibu Creek State Park, Los Angeles. Then it might have looked too much like Korea, or Ape City, or Walnut Grove...
And he also used real N.Y.C. streat locations in his Godfather films. When the film makers try to use locations that are as autentic as posible, I feel it makes the film a bit more special. It adds a great deal of verisimilitude to the piece.