If you are a dictator, you don't really want to have people that you control learn how to question what you are saying. If a person understands where and how to question something, sooner or later a dictator will be in some kind of trouble. Study the last century particularly WWII if you don't believe me. Stalin's regime was a nightmare and we all know about Hitler's and what happen to the third Reich.
No books means no education. No education means no questioning. No questioning means a dictator can lie. Lies keep him in power.