Why is there no universal language?

Languages grow and change as people use them. Since no one speaks to everybody else in the world on a regular basis, changes happen in different directions in different locations. We can notice this happening in the differences between American English and British English and the more time elapses, the more profound the changes. For example, Americans and Britons can understand each other with only a few stumbles. Danes and Swedes and Norwegians can also understand each other, but it's plain that they're speaking different languages. Spaniards, French, ltalians, Romanians, even though they all share Latin as a parent language, cannot understand each other.

Some people claim that there once was a common Earth language, which they call "Nostratic," but if so, it was so long ago that any threads leading to modern languages have been broken.