This is by design. As I mentioned in another comment, there was this 1950s utopian ideal amongst American planners that we'd all own cars, we could live tens of miles away from the city where we worked, modern planning would ensure traffic was amazing, and we could avoid all that nasty density business and all the 'others' that come with it.
No longer would white men have to live near black men. We could all just drive away to the suburbs where restrictive covenants meant we couldn't even sell to black people and restrictive zoning forcing large lot single family homes would ensure that, even if we could legally sell to them, they wouldn't be able to afford to live there anyways.
Racially motivated covenants can't be enforced any longer, but the land use control mechanisms put in place to ensure no poor people move to the pristine suburb still exist.
It is unfortunate that the Supreme Court upheld these laws, even sharing in their legal opinions that apartments are evil and a drain on society, so of course we should ban them.
If they had not upheld these laws, or these laws did not exist in the first place, I'm sure the US would have maintained its public transit friendly character to a great extent. Even LA had one of the largest, if not the largest, rail systems in the world. Imagine that.