Why was is important to have illustrated manuscripts of the bible?

Before the invention of the printing press, all books were manuscripts. These were extremely difficult to make, which made them very expensive. Moreover, because of how expensive books were, and the fact that public education was not available, most people were illiterate (they could not read and write). This meant that they would not have been able to read the Bible on their own. It was important for the Bible to be illustrated because this allowed people to understand and follow the stories that they were not able to read.