These forks (for the most part) occurred organically, not just in order to sound different. After the fact they became a matter of pride, culture and nationalis

These forks (for the most part) occurred organically, not just in order to sound different. After the fact they became a matter of pride, culture and nationalism, but originally they were not. People just spoke in the way that felt the most convenient and pleasing to them, at the time there was no widespread long distance communication and the vast majority of the population never left a relatively small radius around where they were born. Languages diverged because there was no external force unifying them (like, say, the roman empire). Eventually due to the lack of contact languages drift apart and become mutually unintelligible. Imagine a world where there's no TV, radio or internet and you could only travel by horse and most people use the language mainly in its spoken form (if they can even read at all). How long do you think the Australian language would remain unified in these conditions? One generation? Three? Ten?