I think what you mean to say is that there are few "medium" cities in the US where "techie and richer" people elect to voluntarily live without a car.

You absolutely can live without a car in a lot of these cities but if and only if you want to bike. If you want to ride a lot of public transit it's gonna suck.

What you can't do is do it in a trendy way that "befits your tax bracket" so to speak and prevents the white collar types from looking at you like you're inferior when you bike lock your cargo bike to the lamp post beside the liquor store.

As for bigger cities, you absolutely can live without a car in Boston, DC, SF, Atlanta, Chicago, and the list goes on but toward the bottom it's gonna require more biking and less public transit.