The spread of population in Los Angeles, the terrain, and the seismographic picture do not make for a cost-effective mass transit system that would serve the whole area. In most large cities, there is a CBD ("Central Business District") that is the hub of the mass transit system, and all the surrounding areas have service to the CBD. That is not the case in L.A. They do have mass transit, but it serves only a small percentage of the overall population.
Not to mention the car culture, in which people manifest their adopted personalities with their Beemers, Prius's, Tesla's, & whatnot.
Not to mention the car culture, in which people manifest their adopted personalities with their Beemers, Prius's, Tesla's, & whatnot.