I've never encountered a course where it was supposed to be mandatory to use a drop zone as opposed to playing again from the previous spot. I've played course were drop zones existed as a convenience, but never where it was required to use it, and especially never where you gained a distance advantage over where the ball entered the hazard. I know that such do exist, but I've never played a course with one. In the cases where I've used a drop zone, it only allowed you to move forward to some point near the edge of the hazard, but not beyond the point where the ball would have crossed the margin.
My previous club's course starts with par-3 which has a river running across. It is only 120 yards or so, but especially for novices it is scary opening hole.
There is a drop zone provided on the other side of the river, and actually almost on the other side of green for balls ending up in WH. You can of course drop on tee side of the river and pitch/chip, but hitting across river 30 yards to a green which is 10 feet higher is not for all novices. So I guess to make life a bit easier (and faster) there is a DZ. I am not sure if that DZ is used in all competitions, like national match play championships later this summer, but for regular play at least.