Diversity.
It's application in architecture is an essential component in societal sustainability.
Without going into a thorough theoretic analysis: it's apparent in all countries, states, cities, and cultures in general - the quality of our surroundings is directly linked to our built environment.
Europe, in general, and major US cities are great examples of this and yet all too often we find that there is an overtone of resistance to utilize modern methods for new buildings as well as renovations - both functionally and stylistically speaking.
Simply put, we all frequently see people shy away from a solution (building or construction) simply because it is unfamiliar.
Because of this, opportunities which would better accomplish an objective are sometimes missed in order to accommodate a convention which is based on an older culture.
It's comfortable.
Think about it: take technological advancements in the past 10 years; how has the way we live, work, and communicate changed? Because of the internet, for example, and its rapid evolution in accomplishing almost anything, the land line is becoming obsolete, our conduit for instant information has become a screen on our desktops or in our pockets, and we are able work closely with a team physically disbursed across the world in real time.
As a result, it's not as important to locate telephone outlets in every bedroom as ethernet outlets, consideration must be given to the placement of elements which block WiFi signals, and our office spaces may be compact and efficient.
This, of course, is a vague example but buildings which address today's needs have an identity which distinguishes it amongst older counterparts.
So, in essence, we would have older buildings juxtaposed with newer counterparts, each marking its own time in history.
It's this very instance which creates rich communities.
We Americans are often reluctant to change because there is a general fear of nonconformance as we consider resale and, more frankly, the almighty dollar - the resulting form is one which has no real identity because it must accommodate any activity, person, and average functional needs.
Society really doesn't hold a fundamental importance to the long-term impact of our buildings.