When building fronts face streets visitors feel welcomed. When sides or backs of buildings face streets visitors feel ignored. When pedestrians are faced by building fronts they experience interesting views into windows. When pedestrians are confronted with blank walls their walk is less interesting and less commercially inviting. Eyes-on-the-street, the continual surveillance provided by storefronts and windows, also create safer environments.
Building type variety creates places with aesthetic and functional variety. Buildings can be designed to serve a mix of uses such as residential, commercial, multi-use, live-work, and so on. Purely residential places with a variety of building types serve a variety of people. Buildings may also be designed to be re-utilized and evolve over time.