Eddie, I know -- but when my sister lived in Berkeley, which was still a 415 area code back then (510 went live in late 1991 IIRC) I would always dial ten digits, but then our next door neighbor told me she just dialed the 7-digit number to Berkeley so I started doing the same thing and calls went right through. I started doing this for all calls to 415 numbers. I think it was because there were few enough phone lines back when we only had three area codes within the entire LATA, AKA Local Access Transport Area, and I presume there weren't any duplicated prefixes across those three area codes. I think this pre-dated electronic switching equipment, which could have had something to do with it, at least on the originating end of the call.
There are at least eight area codes within our LATA now, and for sure there are duplicated prefixes among them, so 1+ dialing is required. Since 707 has no overlay, it makes sense that dialing 1 wouldn't be required for calls to other 707 numbers. The same may be true of 415, 510, 650, 925, and 831, but since 408 shares the same boundary as 669, 1+ area code is required for all local calls including to other 408 numbers. I'm certain the technology exists to eliminate 1+ ten digit dialing for calls originating and terminating within 408, but Ma Bell sees no reason to offer it. Only the older generation cares, and Big Telco is all about eliminating land lines rather than investing another dime into their continued use and maintenance.
I had a friend who lived in Napa and he said they still had to dial Operator to place long distance calls until 1979. I highly doubt that 707 is that far behind the times anymore, but it does make sense that calling within your own area code would only require seven digits. I've never been in favor of overlay area codes, but in the age of cell phones, the term "area code" has lost all meaning. That's a term that Ma Bell came up with to introduce the new North American (direct) Dialing System to subscribers. There is no such thing as an area code in telco lingo. It's known as the NPA -- Number Planning Area -- which is more applicable in this day and age. And since nobody memorizes telephone numbers anymore (except me, it seems) and just taps a name on a screen, the number of digits required to dial doesn't even matter.