There are other brands of diesel trucks and vans who have it while others don’t. If some brands of trucks and vans don’t have it, then it goes without saying that it’s not important. However, if it’s really important how are these vehicles which don’t have it are able to do away with it without doing harm to its engines.
Yes, the "Sedimentor" sensor light/buzzer in a diesel truck or van is important; and this is because once it gets ‘On’, it is telling the driver that it is about time that you start removing the water/sediments that has accumulated in a special area of the diesel fuel tank.
The only reason why other trucks/vans don’t have this sensor in its dashboard is simply because the manufacturer(s) concern have incorporated the sedimentor mechanism in the vehicle’s fuel filter, such that every time the fuel filter is changed, the accumulated water/sediments are also removed. This is unlike the first type of diesel vehicles I discussed earlier where a sedimentor mechanism is provided and separated with the fuel filter. The rational behind this, other than efficiency, is to prolong the life and utility of the vehicle’s fuel filter.
And by the way, water in diesel fuel is a natural occurrence especially during cold, damp and high humidity.