Walking is, I think, a combination of habit and culture.<p>Both sets of my grandparents, from opposite ends of the country, used to walk quite a lot without any real purpose for doing so. They did this well into their 80s, and so did their friends. It seemed just to be something they did, and always had done.<p>My parents, by contrast, almost never walk when they can drive, and will often drive to a park to let their dog off rather than walk her there and back. Many of my friends are the same. One goes so far as to drive five minutes, then deals with parking and paying for it, to get his lunch every day rather than simply walking for the same length of time -- he spends more time in traffic in his car than actually moving.<p>One colleague of mine at my last job was amazed that I walked from the train station to the office -- a walk of less than 10 minutes at a brisk pace; it didn't even occur to her to ask about how I'd covered the mile-and-a-half from my home to the train station at the other end. My total commute was about the same distance as hers, but it took me less time, cost me slightly less, and got me some exercise into the bargain.<p>Some evenings, my fiancée and I would go for a walk of a couple of miles just to get out of the house, or to enjoy warm weather, or just because.<p>Since leaving that job, I walk less overall. I also have a dog, now, the walking of whom replaced most of the purposeless walking I used to do in the evenings. Most of my walking, now, has 'purpose' because it's exercising the dog, or taking her out for toilet breaks.