For me, it depends on how many different places you wish to go to. When I am in Orange county, I don't usually have a large list of places I am interested in, and thus, a Lyft/Uber/Taxi or ART is the way to go.
Once I go to Los Angeles, everything is so spread out, and I want more flexibility, and thus I get a car. I also happen to know a few people in LA that I would want to visit, so it makes more sense to me in that respect as well. It's hard for me to envisage relying completely on Uber/Lyft/Taxi or other public transportation in LA, unless you are just interested in a really small area of it.