GPA matters whenever someone is trying to further his or her academic career. For some graduate programs, even the highest standardized test score can't make up for a sub 3.5 GPA.
To be fair, I know a bunch of people who got into USC with 2.5gpas
Well, USC is a private institution so they can make exceptions for people with money. Also, USC students are proud of their school but they aren't smug about how smart their school is, unlike UCLA students who act like they went to Harvard.
you act like gpa even matters.
Sadly, it does. Otherwise I would have gotten into UCLA with my SAT scores alone. But noooooooo, "You have to show that you have any iota of work ethic" they said.

You probably should have tried to get even higher standardized scores. Not just SAT but also some 4s and 5s on APs. UCLA is not that selective. My GPA was far from elite but I still got a full scholarship offer because of my test scores.