Well, in all honesty, we teach our children reading/writing at this age (in fact, even earlier!). We start teaching them right/wrong at this age (and wish, they just knew it!!!). We start teaching them basics of mathematics, science and more at this age, don't we? Then, why not communication skills?
Now, when you meet a child does any of the reading/writing matter directly, if the child doesn't communicate effectively? Your first and probably last impressions are formed based on how the child interacts with you and how s/he talks/behaves in a group. It is the same between children too, they weigh and judge each other this way (and don't we too as adults?).
Just like we can embed all these other skills at a young age, we can embed communication skills as a habit at a young age too. If it comes as a reflex to communicate well, it is a part of you forever, right? If you know how to be aware and how to express your emotions, no one can take you for granted or take you for a ride, can they? There is no need to wait till one is in their 20s or even in your teens to learn these. You will have loads of unlearning to do first, at that age!
We teach these concepts through simple, understandable and age-appropriate methods and children learn to apply them in their own surroundings as they learn! Feel free to contact us if you have further queries or suggestions, we would love to help you.