I have had this discussion with a couple of my Norcal friends. They think that Socal residents give the freeways/highways too much respect, similar to how we refer to "the President of the United States" or "the Ohio State University". I think that the difference is that Norcal people consider the freeway numbers as proper names, where as Socal people don't. You don't say, "I'm heading down the Wilshire Blvd", but you would say, "I'm heading down the street" as opposed to "I'm heading down street". Just my .02.

__________________
If you feel the need to bash/rag/insult/demean someone, please read this before you do. Thanks and have a great day!