Actually, LA has a very good public transportation system. It's just bus-based, can be slow compared to driving, and is widely considered as only for poor people. Higher-income people have a strong aversion to taking the bus, even while happily taking subways.
I find that's mostly a function of how spread out LA is. Public transit is always going to be slower than personal transport - it's got to stop every so often, or what's the point? - and that's just magnified by the distances involved.
Also, we don't have great public transit through high-traffic areas from where people are to where they want to go, because we've got this weird kind of medium density continuous sprawl. There just aren't that many of the good high-density locations at which to place Metro stops, although that seems to be changing more because people go "Hey, let's get a stop here, and then we'll /become/ a destination location."
Also, I don't know of any city I've been in where the "Buses suck, subway rocks" relationship isn't true. I don't think it's just a "buses for poor people" thing, but I don't know what's going on to cause this anecdotally widely observed phenomenon.
I bet it's that subways don't compete for traffic, whereas buses have to deal with all the congestion that cars do, in most cases. If my choices are to Drive Myself (my own music, my own pace, no motion sickness, and no uncomfortable staring at the lady across the aisle from me because hers is the only window I can see out of) versus a bus, I'm likely to take the car. This is compounded by not having to __wait__ for the bus schedule.
Taking the Bus + Train from SF to LA area takes longer than driving, and has more stress. Can I stop to use the bathroom, or will I miss the bus? Not an issue if I am the driver. I realize that's not the same as city driving issues, though.
It could be better if Metro would implement a hub-and-spoke system with buses running within local neighborhoods and trains running longer distances. I worked at Metro for a couple years in the mid-2000s. Hub-and-spoke would come up occasionally but seemed to always get beaten down.
