The DFS and the other facilities are often used for testing and/or development of new equipment.
Since we can simulate environments that are difficult to encounter in the real world we have been successful in a number of development projects were it would have been difficult and costly to do it in any other way.
Some interesting areas where simulation would be advantageous, are:
Equipment for use in high-G environments (Aircrafts, Formula 1 cars etc)
Equipment for use in space or any other high altitude area (low pressure).
Rescue equipment for sea survival.
Trying out new equipment in a simulator is a cost efficient and also a very safe way to do things. The risk for serious accidents with severe consequences is much less.