Great thread! First, I believe every golfer should have a choice in how they play their golf, weather and course condition issues excepted. That said, economics will ALWAYS factor into the equation. Some folks simply walk because they wish/need to because their financial circumstances dictate that. Some folks are just thrifty(cheap) and will ride/carry their own even though they can afford to take a caddie when available.
Humans are inherently lazy in the main, and give a choice, will opt for the easier option. Golf, particularly in America, has evolved into cart-ball because the industry folks have, for the most part, totally presented it as the way to go... for a variety of reasons.
Let's put one of the biggest myths in the game of golf to rest...the idea that carts are some sacred cow because they produce SIGNIFICANT revenue for the facility. When you factor in: their cost, the cost of the structure to house them, power costs, man hours maintaining, washing(wasting water!), and repairing the fleet, turf damage, accident liability costs(in the U.S. alone, there is on average, one cart related fatality per week!), costs to install and maintain the cart path most facilities have...that profit center gets MIGHTY SMALL...in a hurry. All of those HIDDEN costs are NEVER in the financial analysis.
As an ardent apostle for caddie golf, I not wade into ALL the benefits that dynamic has AND continues to contribute to the game, but there is no question that there is no comparison when one weighs the contributions to the game made by them vs. cart ball. It ain't even close!
If you love the game, respect it's history, and have the opportunity to play a facility with a quality caddie program...take a caddie. You'll be investing in supporting and sustaining it's most enduring constant!
Cheers,
Kris