I always walked and carried up until 4 years ago, when an injury and recurring lower back problems precluded carrying.
I've taken a caddie at St Andrews several times and thoroughly enjoyed the experience - well worth it, IMHO. I enjoyed the experience - the line from the tee, the approach,reading the putts from a first rate caddie.
I've often taken a cart for the second round of the day, especially if playing a hilly course, seems like my back and legs have a difficult time of it these days.
These days I use a remore controlled electric trolly and I love it. I believe if more courses offered electric trollies in lieu of carts, it would encourage walking, and leave carts for those with medical disabilities.