[epistasis]

Though I do like bars and restaurants, most of my interests are far more obscure, and can only be supported by large numbers of people that congregate in dense areas. For example, the types of science I do requires both high densities of people and attracting this strange subset of people to a few geographic centers.

High density does mean more bars, restaurants, and yoga but it also the prerequisite for highly specialized professions like tailors, rare book collectors, rare tea, etc. etc. etc. Bars and restaurants are the tip of the iceberg, but the rest of the iceberg is a long tail. Just as the internet allows people with rare interests to find each other and talk, high density allows these rare interests to meet in real life and develop face to face relationships.