But the point of a language is not to spread to the most people, it is for the peoples using it being able to use it in a way that makes it possible to communicate with their own in a way that makes sense within the local population, its culture and history.

Different languages have a different learning curve based on what language you grew up with. What is hard for you might be a cakewalk for someone coming from a different language, especially if you are coming from a different family of languages.