I don't follow, are people then not able to choose to live somewhere that has shopping facilities or hospitals that are built so as not to be only accessible by automobile?
No, because no such somewhere has been built in the country in question (US) in the past ~60 years, because the default is car-centric. So you're left with a few uber dense, old, predating automobiles, places. Which are extremely expensive, because they simply do not have the capacity for everyone who wants to live in them.
Suburbs/car-dependecy is a classic case of "worse is better". Its simpler to build and the worst-case suburban sprawl is tolerable, so it proliferates.