i18n. They don't want "MyCoolApp (English)", "MyCoolApp (Spanish)", etc. pollution.

i18n would seem logical. They presumably don’t want an English and a German binary, they want it all in one bundle in one as is common on Mac OS X. (I think that, e.g., Lightroom still has different binaries for different languages, which presumably means that it couldn’t be on the App Store.)