We learn about a culture primarily from the artifacts of that culture. Other things also help us understand a culture, such as rituals, but artifacts are easily accessible and act as a sort of record. They are what remain.
Artifacts of a culture also encapsulate the values of that culture. Each and every one. Some do it explicitly, with insight or a knowing wink. Others do it implicitly, without awareness or intent. Some of those values are aspirational, some we might prefer to hide. Regardless, it is axiomatic that all artifacts encapsulate values. Culture is interpreted by the artifacts of its culture, which in turn are both informed by and influential to that culture. An artifact wraps all of this up within itself.
Architecture is a prime example of a tangible artifact. This is why it is so easy to study it in history classes. Not all cultural artifacts are tangible, though many are. With literature, for instance, the physical book typically has no meaning, it is the idea or ideas contained within the physical artifact that is the true cultural artifact. Other cultural artifacts, such as a piece of music, are even more ephemeral. A score of music can be physically notated, and we can study it and know it, but we will not be able to fully understand a piece of music until it is played. Further, we may never know how it was originally played.
There is nothing ephemeral about architecture, and though there are ideas embedded in an architectural object, the thing itself truly is the artifact. The ideas do not escape the thing. In this way architecture is similar to a work of art. Both art and architecture produce objects that are worth thinking about in terms of how they are made, the ideas that influenced their making, and the meaning their maker was specifically trying to convey. They are things worth considering.
Works of art have the potential to last generations, as do works of literature and works of music. Works of architecture do too, but architecture is a special medium. First, due to its expense it is often considered quite carefully before being initiated. Second, it is rarely the result of just one hand. Many participants have a stake and voice in its production. Third, it almost always has a functional purpose, an intended use.
For these reasons, architecture implicitly embeds the values of a society much more often than it explicitly does. The functional purpose often takes precedence over the architect's artistic desires. Further, even when an architect is given somewhat of a free rein, other criteria still need to be considered, such as the opportunity cost of the project, the public face of the architecture, and the relative permanence of the object.
So, when an architectural object is produced that both implicitly and explicitly embeds our values, it is something to be cherished. When it is lost, a part of our culture is lost.
On the other hand, it is also worth noting that these same characteristics indicate that architecture is a much more difficult medium than art in which to be produce either an explicitly critical or whimsical artifact. Indeed, it is rather poorly suited to these kind of tasks. Even when done well, these sorts of project age directly in our view, from which we cannot hide and with which we must continually engage. Therefore, on those projects where an architect can truly influence the output, it is almost always advisable to do so in a manner that respects the effort and cost required to make some of our largest and most durable objects. In other words, it is advisable to build remembering that the opportunity was a gift.