I don't know specifically about California - but many places around the country - before the officer ever talks to the driver, she/he has notified the dispatcher where they are stopping the offender, the license number and description of the vehicle and the reason for the stop.
If the cop decides to not write a ticket - she/he has to have a reason their supervisor will accept.
Some towns in the Dallas area - officers have a quota of the number of traffic stops they need to average each day. Ticket quotas are illegal, but several officers tell me they have to issue tickets for at least 75% of their stops.
I've never been stopped where I was singled out of a large group of vehicles. But I always remember an old saying from a cop
"Ever go fishing?"
"Ever catch all of them"
