Edit: I guess my point was that from my experience visiting New York that's a city where public transit is so good that a car really seems unnecessary. Someone from NYC might be surprised to learn (or be reminded) that it's the exception, and that in most other places in the country it's a hassle not to own a car -- that's not a problem just in LA.
I'm in Seattle myself (Capitol Hill) and while I could get by day-to-day without a car, it would make my commute to the east side almost twice as long depending on traffic and bus timing, which isn't worth it for me. And while Uber / Lyft are a good alternative, a car is still the most convenient way to visit other parts of the city.
I even did so myself in Tucson for a year, though I'll grant that that was pretty annoying.
Because those are all significantly (hours more) to take mass transit than to drive.
It's very doable to not do cars in Seattle, however. Particularly if you have a car2go or zipcar account!
There are a few decent neighborhoods where one could make due without an automobile but they're pretty expensive (by Pittsburgh standards) to live in. Shadyside and Oakland are two such places. There are a few Hipster enclaves where a fair number of people do it but they're not very common. Outside of neighborhoods like these and especially outside of The City proper, it's a nightmare to try getting around without a car.
Instacart does my groceries and it's only about an hour or so going from the North side to the West side on the "L". Pretty great.
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.
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.
http://en.wikipedia.org/wiki/Orange_Line_(Los_Angeles_Metro)
They run on dedicated right-of-way. Not just their own lane, but their own road. Not as nice as a subway, but approaching it.
If you're into NYC comparatives, its isolation and ethos compares to Staten Island. Lots of cops and firefighters.