In the city where I live (Portland), most people take buses or the light rail when they can't bike due to the rain. In the summer, there's a lot of walking. I've noticed less of it in the suburbs, but there's quite a lot of it in rural Oregon. Simple, cheap fun.
The Buddhists, whom Schopenhauer appreciated and modeled quite a bit of his metaphysical and psychological thinking on, also enjoyed walking a fair bit. The "four positions" of the body for meditative posture, which the early Buddhists reference, are 'lying down', 'sitting', 'standing', and 'walking'. They, the Zen monks, and others involved in philosophical and spiritual traditions, tend to share appreciation for walking forms of meditation, or a love of "pointless" walking, which is meant to foster a more concentrated state of awareness. There's quite a lot of walking involved in the homeless monk's life, as well, as many monks undertake a training rule to abstain from the use of vehicles, undertake a rule to collect food on an alms walk, and may just simply enjoy traveling. Such is the life of a wanderer. Walking on and on can help people drop attachments.
We often see depressed, anxious, obsessive, and manic sorts walking... or more, pacing... which I think resembles the walking of monastics, or shamans, wizards, and priests in "ritual walking". A lot of very creative and intellectual types can be seen to pace mindlessly... can be walking be a source of stress relief? It's a common form of training for the military, and also a common form of punishment for prisons, as marching (perhaps a bit faster pace than walking). But endless walking, marching, and pacing can't be all that good for the mind, as post office workers can "go postal" from too much of it.
Walking mindfully, which can promote philosophical or creative thinking, provide psychological therapy (as Wittgenstein said, philosophy is therapy), or lead to spiritual enlightenment and purity, is as easy as placing all your focus on the soles of your feet... down, down, down, down, or place, lift, place, lift, or left, right, left, right, left, right.