I'd love it if a course got everybody's butt in a cart. As in, a cart for every golfer.
Consider this: After getting the tee time, you wait 20-30 minutes for your turn to tee off with three or four groups ahead. You and I are in a cart, and two of our buddies are in another. You pull-hook one about 310 down the left, and I hit a weak slice about 200 into the garbage on the right. (Or vice-versa.) Meanwhile, the other two guys in our foursome have done the same thing.
So all day long we're driving zigzags across the entire course chasing down each other's golf balls, and in the time it takes to do that we've lost track of where we hit the others, ready golf is completely abandoned, and it becomes a 5+ hour round.
I'd say four decent players could get around in the course in three hours or less, even while taking their time.
Increasing the number of golfers on the course (by speeding up play!) would easily offset the increased fuel cost and maintenance a golf course would incur by putting more carts out there.