We never use the dictionary

"We never use the dictionary" said my Russian teacher today. "What do you mean?" I ask. "When we read a book, we never look up word in a dictionary, everything is clear and comprehensible." So I thought about it and could not come up with a reasonable conclusion. She said, "When I first came to Mexico, I found it really strange that people look up word in the dictionary because they find words they cannot understand, that they have never perhaps seen in their lives!. In Russia that would never be the case. We have no problem understanding every word. It's your mother tongue; you should know it all" Wow, how about that?? I said to myself. Food for thought...