You're only considering the negative aspect of "big words". Sure, there are many instances in which peope unnecessarily use lesser-known synonyms, but it is helpful when people utilize a vocabulary in order to be concise. I think that while the current mantra of "don't use big words so everyone can understand" is called for because of the amount of people abusing vocabulary so others will consider them intelligent, we should remain cognizant of the benefits succinct communication provides.
And it is even more important for precision, when a less common word is closer to what you want to say than a more popular one. This is one point Robert Heinlein made in Expanded Universe when he was defending Doc Smith's "space operas" and the vocabulary that was used in them. (Note that since "the map is not the territory", nothing, not your thoughts or even a physical description, can be exactly captured in words, but that doesn't mean it is not sometimes important or at least useful to try to be as precise as possible.)
