I'd guess that because so many games sold by GOG are from the 80s, 90s, and early 2000s, when the world was a LOT less interconnected -- many developers didn't bother to even consider making localized versions of their games. And when they did bother to make localized versions, the work was sloppy and half-assed. This is why when I see comments like this:
Red_Avatar: Belgium, where I live, rarely has localised games or movies - you get subtitles at most which makes me very happy since I HATE localised stuff....
I so completely agree 10000000000000%. I mean, translated menus and such can be OK, but games start feeling more and more different from the original language version the more they're translated because connotations, expressions, humor, tone, etc. are not always shared across languages. Especially when it gets to voice acting -- wow, I can't even describe how much I hate dubbing.