Finnish, my native language, has this to a lesser extent. Historically, there has been a significant regional variation in spoken Finnish (although modern communications and inexpensive travel have greatly diminished the differences), but the more formal the context, and the more diverse the audience, the closer one's speech tends to the Standard Written Finnish.
To some extent, isn't this true for English as well, at least in the UK? Many regional dialects are almost mutually unintelligible, but everyone understands Standard English (aka Received Pronunciation or "BBC English".) Perhaps in Arabic the differences are even more about vocabulary and grammar, not just pronunciation?