GNU lisense simply states that we should credit Wikipedia. It would be impossible to quote every single editor. The History tab is surely there as a tool against vandalism ON EXISTING articles. As most editors are anonymous, it is just foolish to suggest that every editor be credited. Nobody is saying that the article existed somewhere else or that many editors contributed to it. They use those article in the sense that "this was on wikipedia" but no longer. The GNU lisense covers that.