Yep, trains are >an option<. You don't have to use them, especially if you have to go out of your way to do it. They're a useful option in parts of California because of the state-supported corridors that have multiple daily runs, dedicated buses for a lot of connections, apparently better performance incentives for the railroads (though if Japanese perfection of "on time" is required, well, you need to live in Japan), and California prices usually don't vary much on holidays. Except for the fairly common twofer or family deals, they don't vary much other times either, which means the long-distance trains might actually have cheaper (and more comfortable) coach seats (though don't believe the schedules) sometimes (though never on holidays!).

As for Greyhound, they and Megabus are strictly for-profit, and since buses were deregulated a long time ago they don't serve most of the places they used to. Funny, the fares haven't dropped much as a result of that, and they've abandoned most of their bus stations in favor of curbside stops. Not An Option for most people for most trips.