Why do people have University license plate frames on their cars?

I’m doing a class project on the reasons people display schools on their cars, more towards license plate frames.This is for a class about approaches to cultural studies, and why people do the things they do. My main question is: do you have a WSU Cougar license plate frame or a UW Husky license plate frame? Finding answers to why people feel the need to display a university license plate frame, I can further answer the question of WSU vs UW license plate frames on cars. I have a UW Husky plate on my car,but what is the difference for other schools displayed on cars? And why do you have the license plate frame on your car?