Hope this doesn't turn into a NorCal/SoCal flame war... such is not my intention, although I am a true SoCaler at heart
This is not flamebait, but just my opinion...
But face it, from the perspective of the airlines, SFO has serious weaknesses compared to LAX.
* LAX has good weather year-around, and runways that are properly separated unlike SFO, so delays are rare. Everytime there's so much as a big cloud in the vicinity of SFO, it seems that every flight gets delayed, and ripples throughout the nation.
* LAX has 2 1/2 the population of the Bay Area => more O/D traffic.
* the LA area economy is less focused in the tech industry, so it took less of a hit during the dot-com implosion.
* LAX has airport management with a clue (SFO's new international terminal: signs and announcements in English only in an International Terminal?! Rent for stores/restaurants 3 times the level of the old international terminal, for about the same traffic level?!)
* LAX is not singly dominated by UA, even though they are the largest carrier, unlike SFO (and DEN, IAD, and ORD to some extent)
Look at airlines like Thai, Malaysian, Air New Zealand, Air Tahiti Nui, Air Pacific, EL AL, VARIG, Aerolineas Argentinas, Aer Lingus, Lan Chile, Air Jamaica, China Southern have never served SFO or pulled out long ago (QANTAS, SWISS, China Eastern). As far as I know, none of these airlines have plans to start or resume SFO service.
I'm sure if UA/Star Alliance was building a West Coast hub now from scratch, they'd go for LAX, not SFO.