What is the best reasoning for why many "open-book" exams have "no Google" rules?

I was recently reading a book of philosophy and I came across a quotation that had a footnote citing a Wikipedia reference. The quotation was a reference to a philosopher and I had no idea what is meant. I went to read the Wikipedia article, and even after finishing it I was confused as to what the hell that means. I then checked out the Stanford Encyclopedia of Philosophy article on the topic and found much better. There are numerous resources that Google is going to give that are going to be far superior to a 15 page textbook description of philosophical lists. <br><br>What is the best reasoning for why many "open-book" exams have "no Google" rules?