There isn’t a single use for language. Learning a language isn’t just for communication purposes. Just like a rock can be used for building a house it can serve as a chair. There is no set defined limit as to what something is used for. The purpose of any object is the choice of the individual.
So learning a language could be for communication purposes. But it can also be for honing thinking skills. And there is nothing to stop us from learning a language for both purposes, or even have more purposes.
Why kill two birds with one stone when you can kill three.
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