An intermediate cut might be useful if you maintain very long rough, but at most clubs it fights against the appearance of a nicely defined fairway because the transition between each cut is relatively small. We mow our fairways at 0.5" and the rough is maintained at 2" or 2.25". Additionally, it requires another machine set at the intermediate cut height which in my opinion, are resources better used elsewhere on a golf course.
The argument of fairness, which seems to be, a ball missing the fairway by a foot shouldn't end up in long rough, is a slippery slope. Logically, golfers will argue a ball missing the intermediate cut by a foot shouldn't end up in the long rough etc, etc., until all you've done is lower the height of rough throughout the course and you are back to 2 heights of cut!
Tyler