Why are we using self-driving vehicles as a panacea for historical underinvestment in public transport?
Not saying that they wouldn't play a role in a functional public transport system, they'd be invaluable for the last two miles from your station to your destination.
But while our people transporting systems prioritise roads and cars, we will never have the high quality and safe public transport that high quality of life cities thrive on.
(And while I write this from NZ, with only limited experiences of LA and SF, we copied America, we went for sprawl and freeways, and it's strangling our largest city.)
I know and spend time with people who live in Berlin, Munich and Hamburg, that don't own a car, because they don't need to own a car.
They might rent one for a holiday into Italy, or they might use an app like Lime / Bird etc. to rent very short term a tiny car like a BMW i3 for a big grocery shop.
But because their cities are dense, and mix commercial with residential (e.g., ā bunch of 5 storey apartment buildings with the ground/first floor being commercial, depending on where you are), they can often buy groceries at the local market on foot on their way home from the U-Bahn, or head down to the local Getränkhandel on a bike with a basket or two to buy their beer and bottled water.
Centralising commerce away from residential, especially with big box shopping areas, is predicated on car culture, and bakes in the need for cars.
TL;DR self-driving vehicles alone are a band-aid over an unsustainable transport culture and strategy.
But they'll form a critical part of a sustainable one.