I do not understand either. My father has very, very bad knees....he is going to be 65 this fall and plays 3-5 days per week. He rides quite a bit....but, when we play and its hot enough outside that his knees do not hurt.....we walk. I carry a light Callaway bag with Izzo straps, at 36 I can still do that no big deal.....in 20 years? If I walk, I will probably use a cart.....if people bag on me for using a cart....well, then I guess I do not care....especially when I turn in a sub-80 score!
I like to walk as much as possible....I just feel that it lets me experience the course in a more personal way!