It's one of those stats that just smacks you across the face: In a recent Pew poll, only four percent—4%!—of consistent conservatives want to live in America's cities.

Meanwhile, about a quarter of people with mixed political views want to live in cities more than they want to live in small towns, suburbs, or rural areas. And nearly 46 percent of consistently liberal people want to live in cities.

For someone who writes about technology, this is particularly significant. It's not just that the latest round of hot companies are deciding to headquarter in cities like New York and San Francisco; it's also that many of these companies make sense, for the most part, only in urban environments.

All the startups clumped under the heading Uber for X—of which there are dozens—require high concentrations of people (i.e., cities). Take companies like Airbnb, which works best with a lot of listings in a given area, or Yelp, which declines in utility as fewer people contribute reviews. But take, as well, the range of other technologies that make the most sense within dense agglomerations of people. The most prominent example is autonomous vehicles, which require detailed, expensive, and regularly updated maps to operate. For that reason, those vehicles will almost certainly deploy in cities first, and maybe only in places where enough people drive to make the investment in mapping the area worth it.