That's great, but in the case of zip files it's because the file and compression format hasn't materially changed since the 1980s, and in the case of Excel because Microsoft controls the format. Apple does not control the Stuffit format and never has (and AFAIK never distributed their own software using Stuffit). Stuffit's compatibility issues are due to the people who make -- or at this point, I believe made, past tense -- Stuffit.