Thats true, the whole system of writing is poorly taught. The purpose of writing is to convay the meaning in a suitable manner - but, what exactly is a suitable manner? Well that depends on a variety of factors such as the intended audience, subject, purpose of writing, technicality, etc. There just isn't a singular lexicon (dictionary) - as such, reverting back to more generally known words is better design than using unrelated lexicons.

In addition, general lexicons may have issues with ambiguity. But they also can be explicitly defined using contextual cues. The point in writing is so its understandable not extravagant.