The purpose of the F-117A never was to deliver a nuclear payload. In the Cold War days it more than likely would not have gone nuclear instantly. The job of the F-117 then was to penetrate the comprehensive radar network to deliver a presion strike on a target of value. These targets would include bridges, fuel and weapon staging areas, air-defense network C3I sites and other command networks sites. These targets would be well protected but not worth using a tactical nuke on. Thus the outcome of all of this would be a degraded command structure reducing the operating capability of an OPFOR. Also these aircraft require less support so they act as a force multiplier. The birds have been flying almost 20 years now and it's not surprising that they want to retire a few.