There is a fallacy in some prior posts that it is wrong to criticize the use of carts. If one is physically unable to play golf without the use of a cart, then a cart is wonderful. If one feels the weather or the course layout makes walking not a viable option, then the cart could be seen as the means towards being able to play a round of golf.
However, I do not accept that walking a round of golf for a typical person, on a layout which does not have an abnormal amount of walking distance between green to tee, when the temperature or heat index is not greater than 90 degrees can not be considered as relaxing. Once one becomes a regular walker of at least 15 minutes per day, and keeps oneself well nourished and hydrated, walking 18 holes while carrying a light bag or pulling a cart will not be tiring. And if this done on a regular basis (once per week in season), 18 holes walking will soon become a breeze.
Beyond this fallacy, there is harm to using a cart. First, is the health benefit of good exercise the cart user is denying them self. Second, the cart damages the course and this cost is incurred by all golfers, Third, cart paths are a detriment to the architecture of the course and can adversely affect some offline shots. Third, cart paths add to the cost of construction and maintenance. Fourth, and not least, use of carts requires use of either electricity of gas. These are scarce resource whose production is adversely effecting our environment.
This is why walkers are so aghast at seeing many healthy people riding carts on average courses under average summer weather conditions. This cart usage adversely affects the walkers, but the walkers are not adversely affecting the cart users enjoyment or cost.
Finally, those who walk know that a round of golf is always more enjoyable walking than by cart as long as that person is physically able to walk. The course contours and layout are better realized by foot, the golfer's tempo seems to be better when walking, the mental preparedness flows better from shot to shot when one walks between each shot, and the camaraderie between players even seems to improve.
For further understandings about the benefits of walking, read the chapter in Golf In the Kingdom concerning walking. Also, read Thoreau’s essay Walking.