I am a California resident. I applied to twenty-four schools (including all the UCs), got fourteen interviews, seven acceptances, and six waitlist offers (that I ended up refusing before they came to accept or reject me). Only one of those fourteen interviews was a UC (it should be obvious given my sig which one that was). I attributed it to the fact that, while I was a strong applicant, I lacked any and all research experience. I'm very focused on clinical medicine, so it makes sense that the UC that is most focused on clinical medicine as well chose me in return.
Oh yeah, and the fact that the UCs get thousands and thousands of applications for their five relatively small classes might've had something to do with it as well.