I just wanted to say that I have a degree in English, work with writing in my job, and I use a dictionary quite often.
Yes, I can infer a word's meaning by context clues, but why just guess? You'll be surprised how many people think they are using a word correctly, but are misinformed. I see that a LOT in business writing.
I think it's silly for people to look down upon those that need a dictionary, no matter the book they are reading.
Even the book "Twilight" was well-known for having quite a lot of SAT words in it.