That's really the reason it's there. When you size your force, depending on what kind of a threat you size it against, there are additional aircraft required for attrition losses. This particular survivability feature—and it's only one of many on the airplane—is there to ensure that you have survivability, along with the other factors that go into calculating your force level. Without it, if you're looking at the threat environments that generate the requirement for F-35, you're going to have to buy a lot more airplanes than 65, just because of the losses that occur and that we don't expect to see with the F-35.
So I think that safety, the ability to return home, and the ability to effectively use the airplane in a high threat environment are all reasons why we do this.