I believe it has a lot to do with the attitude most people in California have towards extracurricular activities- here, it's a little odd when all you do is go to school. Most Californian teenagers I know are very much focused on where they're going after HS. Academics are very important. I'm fairly involved in Boy Scouts, so I make trips around the country to work for groups who need it. Californian Scouts (whom I just visited in San Francisco) are the ones who have struck me the most out of any group I've ever worked with. For a significant portion of these young men (and now women!), they are not there to have fun. They are there to add to the resume. On top of that, there's not a whole lot of them. Scouting in general is very small there.
Rambling about a completely different activity aside, I know it's all very anecdotal. That's just personally what I believe.