Well, first of all, we call the region "the San Francisco Bay Area," not "the San Jose Bay Area," so it makes sense to call it "the San Francisco market."
Second - if you look at a map of the 9 Bay Area counties, most of the population is to the north - nearer to the city of San Francisco, than to the city of San Jose. Consider the East Bay cities (Oakland, Berkeley, etc.), the San Mateo county cities (Daly City, etc.), and the counties of Marin, Sonoma, and Solano - the majority of the population is considerably to the north of San Jose.
There's a reason that KNTV (licensed to San Jose) moved their transmitter to Mt. San Bruno, between South San Francisco and Daly City. It was so a larger portion of the Bay Area population could get their signal over-the-air. I can see KNTV's tower from my San Francisco neighborhood (Bernal Heights) only a few miles to the south.
Here's a map of the 9 Bay Area counties. San Jose is not listed, but it starts at the southern most tip of the Bay.
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