^I blame hollywood with the false advertising about the amount of pretty women represented in SF.
since SF is a great setting for a movie, naturally they are going to put in pretty hollywood actresses as main characters.
i guess it may have started with Kim Novak in Vertigo? - ironically her character a pretty blonde ends up not actually being pretty in the end (spoiler!).
others portrayed as natives in SF movie settings: Anne Hathaway (Princess diaries), Jennifer Lopez (the wedding planner).... take note... both are native new yorkers who's beauty archetypes are quite common amongst the crowds (curvy Puerto rican beauty and anglo/plain statuesque preppy pretty girls are a dime a dozen in the city)