Please keep two things in mind:
1. There are only three people who could speak for the developer, Hot Start, and you won’t often see them responding on these forums. Only they can speak to the reasoning behind every decision made for the product. Most everyone here is either a volunteer or a community member just trying to help out their fellow simmer with how things are.
2. However, the main principle to consider why something might be how it is with the product is that the developer is trying to simulate the real life of a Challenger jet and their pilots. As Prefect99 says, it would be unusual for an aircraft to have literally zero fuel in the tanks. Fortunately, the state saving/restoration system is powerful and versatile, so pretty much if you can get the plane into a state one desires then it can be saved and reused in the future.
Hope that helps.