California fishing is regulated by the California State Department of Fish & Game (DFG). You'll seldom see DFG officials on public piers, except to help out, host fishing events, and donate their time to fishing derbies on public piers.
The absence of the DFG employees is because of a law that allows the public (anybody --resident, tourist, any age) to fish off a public pier in California for free. You do not need a license, and the only restrictions you must adhere to are the regulations other fisherman who catch fish in the Pacific Ocean must follow about size, bag limits, etc.
Don't let the thought of size and limits scare you. When you decide to try out fishing for the first time, you can ask somebody else fishing, or you can ask at a bait & tackle shop. You're going to need some bait to get started so you might want to begin at a store where the pros can tell you how to begin turning an interest into a lifelong passion.
Many families take their kids fishing on California piers and the kids hang out for a few hours, even fishing themselves. The entertainment is free and gets the kids out in the fresh air enjoying the ocean, learning about the lifecycles, and maybe growing up to become fisherman like their parents.
Throughout the year you will find fishing derbies on many piers in California. Huntington Beach features a Huck Finn Fishing Derby in August and Seal Beach Rotary sponsors a kids fishing derby on the Seal Beach Pier.