It's not just tipping golf carts. There are max slopes you can maintain bent fairways for example. I measure areas of stress on my courses. For bent, its about 22%, depending on the transition blend at the top. I try to max out at 20%, to give some sluff for construction crews. Bermuda can be steeper in general.
For bent greens, at lower cuts, its about half that. Anything steeper dries out, has mowers on a turn with blades slightly digging in, and may be in a traffic pattern. Those combination of stresses nearly always lead to bad turf patches that supers and golfers hate.
And, as noted, its really the transition from flattish green to steep bank. It needs to "swoop" up to avoid mowing problems.
So, why build in a perennial maintenance problem if you can avoid it? We end up with a few even trying to avoid them.
As to rough and ready, I always thought that some of my courses (like the MN ones) were successful precisely because they weren't overly cleaned up. Golfers heading to the north woods aren't expecting Augusta National and the rougher edges fit the terrain and the image of what the place ought to be. Also, the business model has to be pay to maintain what golfers like most (i.e., greens) and let edges (like cart path edge trimming, outside paths, etc.) go a bit with occasional maintenance, not wall to wall pristine.
As to planned obsolescence, there is some of that, but not the way Sean proposes. Take the housing course whose initial job is to sell real estate with shadows, bunkers, etc. Once the houses are sold, the function of the course changes to everyday members or public course, and the steep shadow banks and numerous bunkers come out as they frustrate golfers. Other courses change, too - from failed high end private to low end public, and must change as well. You could even say changing economic conditions (like the depression and great recession) change the needs of the course, as redesign can streamline some costs.
The length issue may be over, and 99% of golfers aren't affected.