Critical question about freeways: Why do people...?
People in Northern California** just identify a freeway by its number or name alone. (We also use names, but not as often: Bayshore Fwy, Nimitz Fwy, Redwood Hwy, Panoramic Hwy, etc.)
So, what's the deal with the "The"? ("The" as in "duh", not as in "thee".)
*For what it's worth, Southern Californians used to refer to their freeways with names (Long Beach Fwy, Santa Ana Fwy, San Diego Fwy, Golden State Fwy), but that practiced has ended. I suspect all the radio traffic reporters needed more time to deal with the increasing number of traffic events, so they dropped the naming convention.
** just to clarify, nobody up here calls it "Nor Cal" except for people from So Cal and The Valley.