Simply put, Torrey Pines is a "good" golf course IMHO. It can't hold a match up to the inferno that is Riviera.
Torrey is attractive on many levels that have nothing to do with golf course architecture. Parking, access, location, local community and their cooperation, an extra course on-site for tents, etc. Basically, it's logistically easier to host an event there than Riviera.
The "public golf course" angle is laughable. Torrey couldn't sniff Bethpage if it were blown up and MacKenzie were revived to build a new course there.
Oh yeah... plus all those involved in the tournament can go get fitted at Callaway, Titleist or TaylorMade just up the street in Carlsbad and then shoot on down to TJ to go to some donkey shows and observe a drug war first hand. It's all about perks my friends.
Jeff F.