Why vernacular literature eventually became the preferred way to produce books?

I believe the answer is: It became the prefered way because everyone would be able to understand the works and it a had a much larger audience

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Vernacular literature refers to the literature which was written using the language that commonly spoken by local people. Prior to the development of vernacular literature, most of the literature were written in Latin and only Scholars typically understand latin language.

silk

indigo  

rice

all the other answers are wrong