>>28497398And more seriously, fuel per distance is like fuel per time. If you know how many hours you want to sit idling or how many hundreds of klicks you want to travel, you multiply (easier than division) and get the amount of fuel you need for the task. And usually it's easier to get the exact distance or time spent than the amount of fuel, either in the tank or already used, because the data the car can show you is way less precise.
Distance per unit of fuel is good if you know the exact amount of fuel but want to know the distance, and that's kind of backwards. My goal is to get to the known destination, not to drive as far as I can on a full tank. Again, all this is based on the fact that it's easier to multiply than to divide.