As has been pointed out, engine braking is really only required in a car with inadequate brakes. It was popular, therefore, in the '50s and earlier when most cars sported weak drum brakes, and is a technique that has little requirement on the road today except for the drivers of Artics, who will find their brakes to be marginal when going downhill. Engine braking, as an emergency procedure, may save your life one day when your brakes fail or you manage to boil your brake fluid on the road, but in normal driving it has no huge use, like heel-and-toe, which lost its neccessity with the introduction of synchromesh. All the driving instructors I have sat next to have always taught to decelerate with the brakes, and only select the required gear once finished with braking. Effective compression braking was never encouraged. Keeping both hands on the wheel while braking was deemed more important.
It is worth noting that Colin Chapman of Lotus actually went to the effort of developing their famed "queerbox", as mounted in the Lotus 79, to freewheel under deceleration, to avoid compression braking. His reasoning was that the effect of compression braking changes with engine revs, making it an inconsistency that his drivers could do without when on the limit of braking adhesion. Again as has been mentioned, he was effectively saying that the brakes are there to slow the car down and the engine is there to speed the car up.
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