I work in L.A. and man you see UCLA and USC alumni license plate frames EVERYWHERE! However I have to make a case for Cal Poly... gotta show a little bit of alumni pride, y'know? So here goes...
My theory is that both UCLA and USC are big-name schools. A lot of people from all over the place live there temporarily while they get their education. This means a much higher percentage of students live on campus. The university has a captive audience here. For lack of anything to do they attend school events (a lot of students don't have cars). That's where they brainwash you!
CPP is pretty much a commuter school. I personally lived in the dorms, but the vast majority of students lived off-campus, outside of university apartments. These people are not going to be willing to drive all the way from who-knows-where to attend some event. So they escape the brainwashing.
I know my theory is full of holes, but hey, I'm not a scientist.
It's like ak said, you don't have to be proud of your school, but DO be proud of your education!