Density is good for the economy, for human creativity, for the environment, and for this...

There is a long tradition in America dating back at least to Thomas Jefferson that suggests people will be happier in more pastoral, less congested settings with their own space. There is also a long line of thinking that sees crowded, dense urban centers as the source of anxiety, agitation, unhappiness, even pathology. But that is not at all what we find. Instead, happiness levels are modestly associated with density that is more concentrated at the center of the city.
And not just happier but, as Edward Glaeser points out in Triumph of the City, healthier. So, build up and pack the humans in the core.