Look at any pair of range towers and the rear one is higher. People assume it is because it is further away and needs the extra height to stay visible. That is part of it, and it is the less important part.
The real reason is sensitivity. What the mariner is judging is the vertical gap between the two lights. On the centreline that gap is zero, or as close to zero as the surveyor could manage. A boat's length off to one side, the gap opens by some amount. How large that amount is, for a given error, is what decides whether the range is any use.
Two things control it: how far apart the towers are, and how much taller the rear one is. Increase either and a small drift produces a visibly larger separation. So a range built for a narrow dredged channel, where being fifteen metres off matters, will have its towers set well apart and a pronounced height difference. A range marking a broad approach can be much more relaxed about both.
This is why range towers so often look wrong in photographs. They are not composed. Their proportions are the output of an equation about how tightly the channel needs to be held, and the equation does not care what the result looks like from the shore.
It also explains the awkward siting. A rear range is frequently standing in somebody's field, half a mile inland, apparently unrelated to the water. It is exactly where the geometry required it to be, and nowhere else would have done.