The JUCO situation in Southern California is really tough on both fronts. The baseball teams are loaded with lots of D1 talent players who did not make the grades to play D1 and are now trying to get there. A kid who is not a top baseball talent is not likely to play much. And then many of the core classes are filled with lots of motivated students who either could not get admitted into the increasingly competitive UC and State schools (despite many having high GPAs and test scores) or really bright kids who do not know what they want to major in so they go JUCO to save money while they sort it out. Thus, there is a lot of competition for the grades too.
That combination makes JUCO no fall back for many kids who want to play baseball while building up their grades for later movement to a D1.