Mike,
What part of the country and what types of courses. Like Tom says I can't recall coming across a course without golf carts.
There was a (recently NLE) Par 33 nine-holer near my house that had six Par 4's under 380 yards and three Par 3's. It was built on about 30 acres total including the driving range yet I'd say about a third of the rounds played there were in carts. It seemed quite odd to see a perfectly healthy, athletic 16-year-old kid carting around a course on which I can play nine hole walking in less than an hour.
I think nine holes there used to cost something like ten dollars to walk plus another nine dollars for the cart. So it's easy to see why they had the carts, it doubled their revenue and I doubt it doubled their costs.
Oops, our posts crossed.