You didn't, but I did. Like any place, Americans have a culture of their own, and car ownership is a big, big part of that culture in most of the country. (Similarly, owning guns is a big part of that culture for a large fraction of the population.)

>When a person moves from a place with bad public transit and walkablity to place with good public transit and walkablity it is likely that they'll go car free or at least use their care much less. Same applies the other way around.

Well, of course: people have to be practical at some point. Someone moving to a car-bound hellscape is going to need to get a car to have an enjoyable life, and someone moving to a dense city where car ownership is extremely expensive and inconvenient is likely to not want a car at all. But people don't just randomly move to these places: they move there because they want to for some reason, and the ubiquity (or not) of cars is probably a big part of that reason for many. People who absolutely love driving everywhere and hate public transit aren't going to move from suburban USA to Manhattan or Berlin or Tokyo, and people who like living carfree in major cities aren't likely to make the reverse move unless there's some huge incentive (high-paying job, family obligation, etc.) and even here they're probably not going to be too happy with the change.

I really feel like a large portion of the pro-dense-city people really think that almost everyone really secretly wants to live this way and only buys into car culture because it's forced on them. While growing up in a particular environment obviously has a huge effect on your personal preferences, and people sometimes change their opinions after seeing or experiencing a different environment, I think they're discounting how many people really do like car culture, even after seeing the alternatives. My view is that car ownership is a luxury, and a car-based society has huge economic and ecological costs and is ultimately unsustainable outside of rural areas, and eventually more-efficient societies are going to outcompete car-based societies (or, they'll both be destroyed in an ecological collapse leading to general societal collapse). I think we're already seeing a lot of this with the US, where labor costs there are absolutely insane compared to the rest of the world.