They were seaworthy enough to be useful for a brief period before better stuff got developed.
The F-117 could barely fly. The goal was the least radar-reflective plane they could possibly make. They started with an ideal shape that was completely unflyable. Then they modified it the bare minimum necessary to make it flyable, keeping as much stealth as they possibly could without automatically killing the pilot.
Needless to say, it got obsoleted pretty quick. But for that brief period of time where it was the only plane that could do that job, it was magic. To me, the F-117, the Surcouf, the PBY Catalina, and helicopters are all in the same category: Woefully inefficient solutions that are still ******* awesome because the need is real and they really fill the need.