Answer: Indispensable
While I would never force someone to take a cart if I owned a course, it would be financial suicide to prevent someone from renting one. In my old group in north Texas, a full half would not play golf if required to walk during the cool weather months of the year, and probably 80% from late May through mid-September.
Matt Ward says: "Mike, just realize if carts were outlawed tomorrow -- the courses would simply raise the base rate to play to make up for the financial shortfall." Then he opines: "As far as percentages are concerned -- I'd dare say at minimum impactec would be no less than 25% to as much as 50% -- possiblly even more."
If courses lost 25% to 50% of rounds (and maybe more if commited riders tend to play more rounds than walkers), then it would be impossible for the operator to raise the base price to make up for the loss of cart revenues from a mandatory walking policy. It is really very elementary economics, which the "deniers" simply choose to ignore.
Course operators know the economics of carts very well. Riders know that they subsidize Kavanaugh's cheapos. As a charter member in this group, I am thankful for those folks who willingly pay $15-$20 extra to enjoy the same course I do, typically play faster, and sometimes fill in divots with sand that walkers create and leave unrepaired.
Whatever compaction and other damage carts are responsible for, I suspect that cart fees help fund the employment of two, three or more maintenance employees at many courses. The "operating margins" in the 40% to 60%+ range of the cart fleet probably make it the # 1 profit center of a golf course. With very few exceptions, golf courses which enjoy good economics are better cared for than those on the brink of bankruptcy. Rather than condemning carts and riders, we should think of them warmly as we gather around for the Thanksgiving feast.
As to carts ruining the game and caddies being virtous, that's nonesense. I've played a couple of world-class, breathtakingly beautiful courses and the entourage of four players, two to four caddies, and a couple of spectators made it look like a firedrill. Choice is beautiful, though I do ascribe to the right to association. Golf has much bigger problems than the use of golf carts.