Since I've been thinking about cities (and planning to fit realistic future cities into my fiction), I've also been thinking about buildings, more specifically domestic architecture.
Consider the humble single family house. In my town, Cambridge, single family houses are relatively rare: only 14% of the housing stock consists of them. In Manhattan, obviously, the number is far lower. But in much of the United States, single-family houses are the order of the day.
On my shelves are a number of architectural field guides. One I've used, both for touring and for realistic portrayal of period houses in fiction, is Virginia and Lee McAlester's A Field Guide to American Houses.
When you look through it, you see specific regions and periods of style that architects and builders worked within. Some of this was based on the requirements of local climate (rain, snow, heat, etc.), as well as local material (brick, stone, wood), but much of it was just style. One builder trained with another, clients saw houses they liked and demanded ones that were similar. And these styles lasted for quite some time. You see a Greek Revival house in my neighborhood, you can peg it to the 1830s or 40s. An elaborate Queen Anne Revival from the 1880s to the turn of the century. What I learned to call a foursquare ("Vernacular Prairie Style" according to the McAlesters) is more common in the Midwest, where I grew up, than here in New England, but you're looking at something from the turn of the century through the 1920s.
The book peters out after the Second World War, leaving what the book somewhat wanly calls "Neoeclectic". And so it has been ever since.
Now, I'm not writing this to bemoan the loss of classifiable domestic archictetural styles (or at least, not primarily). it's just that, once you see the consistency of these styles specific to certain times and places, their disappearance is worthy of comment.
That's not to say that a tract house in 1955 is the same as one in 2005. Clearly there are differences. But they are mostly in terms of size (both of living space and garage space) and function (bathroom equipment, indoor gyms, entertainment centers). The applique ornament of pediments, columns, and mansard roofs gets smeared on in pretty much the same way over that time. Not a single one of these house's is worth a second's detour to look at--and I am an avid architectural hobbyist.
Fashions change more and more quickly as time goes by. The reason there are so many "revival" styles in our popular culture, is that in the past a style had a few years to elaborate, sink into people's lives, get associated with events and personalities, and appear in literature, books, and movies. Do styles now change too quickly to influence houses? You can get rid of a pair of jeans of outdated cut or a poster of a forgotten band, but what do you do with a house? It continues to proclaim your outdated taste for decades. Better to have a generic non-style, one that has cut itself loose from any specific history.
Or is there some larger cultural change at work? Does architecture no longer speak of us to ourselves, and of ourselves to others? If so, why? Is it because we spend most of our time inside watching one screen or another?
Where do I live? The house I own was built in the 1930s and is of no particular style that I can detect. It has side gables, and a slight overhang on the roof. My invaluable Survey of Architectural History in Cambridge: Northwest Cambridge classifies the houses on my little street as "suburban homes built in the Depression years", which isn't much more than I already know.
Before the house, I lived on the third floor of a 1920s triple decker (a local form of multifamily housing that has served as the first dwelling for many new families). It had square columns separating the living and dining rooms, hexagonal panes in the bowfronts, elaborate door and window trim, and a built-in hutch (another common local feature). It was the most beautiful place I have ever lived, but too small for our growing family. I love my little house, which I've done a lot of work on, but I still think of that sun-washed apartment. An elegant space is not to be undervalued as a source of happiness.