> The 1-income family or single person can simply move as needed.
Move where? I've known plenty of both singles (white collar, blue collar) and married couples and on reflection every single one of them is living and working in a place principally because of job opportunities, not according to their preferred locale. Likewise for families. Many have relocated several times in the past 10 or 20 years.
I think it goes without saying that the unwashed masses the world over will choose larger accommodations (up to some limit), all things being equal. You can't go wrong assuming the masses will choose more for less. I used to think otherwise until I began reading that even the French had begun leaving their small walkable cities for either the major cities or suburbs. That's when I had to face the reality that the French are no different than the Americans, who are no different than the Nigerians.
Given the universal pressure to spread out (at least in the aggregate), if we want to explain trending migration patterns the controlling factors are almost certainly going to relate to the more mundane economics of housing prices and employment opportunities. Those are the relevant variables, everything else is relatively fixed by comparison.
All the other narratives, such as the supposedly unique Millennial preference for urban environments, seem hopelessly tainted by the culture wars. I have my own opinions and anecdotes on the matter, but I've come to think they're largely irrelevant. Why resort to them when the more obvious explanations are not only sufficient to help explain the trends, but also have greater predictive power.
Also, FWIW, I've noticed that our perceptions of suburbia are changing. What constitutes suburban development these days would have been considered overly dense and undesirable by suburbanites 20-30 years ago. I mention that because I think people will rationalize the choices they face and the choices they make. If they prefer suburbia, they're likely to perceive themselves as in suburbia and describe their surrounding as suburban even when their community is better described as more urban. People have preconceived notions of what urban means that don't suffice to explain contemporary patterns of development. I have a two-car garage in the San Francisco Richmond neighborhood in a house that, when built in 1926, would have been squarely considered suburban--presuming the term had been coined at that time. Today most would consider my neighborhood urban, notwithstanding the absence of skyscrapers, but there are plenty of new developments popping up that people describe as suburban but which are not appreciably less dense than many neighborhoods in San Francisco.
But, again, we needn't delve into that minutiae if we instead look to more fundamental and objective qualities, such as cost of housing relative to distance to labor centers. Do I prefer the ideal of the city, where my kids can walk to the neighborhood school, library, movie theater and church, more than the idea of their ability to frolic in open pastures and virgin forest? I realized several years ago that it doesn't matter what I would prefer because the next time we move, if we move, I'll not likely have the privilege of choosing between such stark choices; rather, the reason for moving (i.e new job) will almost certainly narrow my options down not only to a particular city but to a particular neighborhood.