https://en.wikipedia.org/wiki/List_of_U.S._cities_with_most_...
https://en.wikipedia.org/wiki/List_of_U.S._cities_with_most_...
And if you don't need a car to commute, it is weekends that are mostly the issue. Of course, people can always rent but that gets to be a hassle if it's every weekend or every other weekend. It also gets back to culture. As an adult, being that person in a group who always needs a ride gets old after a while.
You're also correct about the shuttle buses. Those were unheard of when I first started working at a computer company on 495 in the 80s. Boston and Cambridge, as well as attitudes about city living, have changed a lot in the past 2-3 decades.
When I first moved back to the area after grad school, some people I knew lived in the city but not many. It certainly wasn't the norm.