Well sure but you're making my point. Silicon Valley has non-tech businesses too like Survey Monkey which is about as high tech as Yelp, i.e. not much higher tech than a Cheesecake Factory (who has a lot of computerized supply chain).
The point isn't to have a pissing match. I'm simply pointing out that the heavyweight tech region is the San Francisco Bay area but within it the tech influence is unevenly distributed which should hardly be remarkable.
It's easier to find marketing, PR, non-B2B sales folks, web designers, ruby developers etc in SF than down here. It's way easier to find people down here who understand interrupt latency on 32-bit arm cores, oddities of device physics below .14 nm, B2B BD folks and the like. Does one diminish the other? No.
Reporters from outside of course go to SF to report because, frankly, what's to see in Palo Alto? I have lived in Palo Alto for decades and yes, apart from the work (which is awesome) it's dull compared to SF, or even to many places lamer than SF.