It's funny you posted this because I was just about to post something similar. I used to walk all of the time, but at my current course the cart is included with membership, so I've been riding mostly. I like to play early in the morning, and lately I have been paired with a guy that I don't enjoy playing with. I won't go into details here and derail the thread, but all of the other members refuse to play with this guy. But every time I show up in the morning, he's there waiting for a partner. This weekend I pondered how best to tell this guy I don't want to play with him anymore. I've been thinking I need to walk more, so I decided I would walk during the week. There is no way this guy will play with a walker.
So this morning I walked the back 9 (due to a tournament I couldn't play 18). I forgot how nice it is to walk. Birds were chirping, bobcat tracks in the dew on the fairway, the whole bit. And I played pretty good and got done in an hour and a half.
I'm lucky that my course lays out very well for walking. A lot of courses don't. Also, at most courses, the pro gets a piece of the cart rentals as part of his compensation, so it's not in their interest to encourage walking.
So I'm with you. Don't walk because "you're supposed to", but if you are under 60 and want to lose a few pounds (and maybe improve your golf) give walking a shot.