Well, what is now the EU market wasn't fully integrated into the "single market" until 1993, well after Unix (from which MacOS is obviously derived) and Windows

Well, what is now the EU market wasn't fully integrated into the "single market" until 1993, well after Unix (from which MacOS is obviously derived) and Windows OS's were starting to be developed. As others have said, trying to target all those different countries and languages is not that straightforward, but it was significantly harder 30 years ago.