When you look at a particular building, all you can see is the finished product. There are no semi-erased lines on the floor showing where the walls would have been, before the architect revised the plans. Architecture is a process that leads to a product. To the viewing public, there is only the product. But to the architect, it is all about the process, and once the process is complete, the architect moves on.
One of the things I enjoy most about teaching drawing to young architects is that the process of creating architecture is fundamentally based on drawing. It's what we do. Novelists write, painters paint, architects draw.
Drawing is the primary means by which we communicate our ideas. When the students pin up their final designs for critique at the end of the semester, I think it's important to point out the examples of students who have design concepts that are beyond their ability to depict via their drawings. This gives me the opportunity to give one of my favorite mini-lectures: That your ideas are only as good as your ability to communicate them. It doesn't matter, in the end, how brilliant your ideas are, or how brilliant you think they are. If you can't communicate them with the world in an intelligible way, you fail.
We also draw to study the world around us. This type of investigative drawing is similar to, but distinct from, design drawing. There is an exhibition running through July 1 at Lori Brookstein Fine Art, in New York, of some drawings by the great architect Lou Kahn. The drawings on exhibit are sketches from his travels, of the 'investigative' type. They strike me as being much more about the process of investigation and discovery, than about having anything to do with making a picture to be framed and hung on a gallery wall. The gallery has the exhibit available online; I encourage you to click through the link and check it out. Better yet, go see it for yourself if you can.
I think if more people saw drawing as a process of investigation and discovery, and less about trying to make a particularly nice looking picture (and by whose standard, anyway?) you would see more people out and about with their sketch pads and pencils in hand. Drawing is a language of communication -- whether you are projecting your own fantasies to show others, or privately exploring the world around you. Each of us has a unique, individual voice, which can only be discovered by taking pencil or pen in hand and doing the work.
Imagine how the world opens up to an adult who is illiterate and then learns to read and write. I would argue that there is a similar expansion of one's life available to the person who is willing to make the effort to discover his own visual voice, and learn to use it to express himself.