Not sure, but it had to have come about via the USGA and US Open or at least the PGA tour, to promote "proportional punishment." It seemed like a logical evolution - as fairways got narrower to reduce maintenance costs, was it "fair" to hit a formerly decent tee shot that used to find fairway and find it in 3" rough". So they came back with an intermediate strip that was less expensive to maintain than fw (theoretically) and less punishing than rough.
I have no real problem with it, although most courses ought to just mow their rough down to 1.5-2" rather than 3-4", if they don't already. Isn't all the punishment you really need a slight loss of spin and distance control?
I tried to experiment with variable width intermediate cuts, based on a strong Art Hills hole I saw once. Seems like, if in addition to your key fairway bunker, the step cut was 2 yards wide on the desired side of the fw, but 10 yards wide on the safe side, it might affect how you decided to play your tee shot.