Lots of more precise words are not particularly 'big' words. One shouldn't have to pre-edit one's thoughts to pull out the better word because it doesn't fit into a typical 5th grade education.

I love older British children's literature because it doesn't do this at all- it expects the kids to learn new vocabulary along the way. Check out 'Peter Pan'- the verbiage is no different than if it was targeted to an older audience and the better for it.