No one has to be taught to comprehend a picture. Children at a very early age can associate a picture of a familiar object with the real object and call it by name.
Text is by no means a native method of communication.
Learding to read and write is laborious and takes several years of learning and practice to acquire a creditable skill. Some people remain illiterate or semiliterate throughout their adult life, although they can perceive the content of a picture immediately. This is why pictures have so much more appeal than written text. Although I am congenitally and totally blind, many of my mental activities are visual. When I read with the Optacon, the point appears in my mind's eye as black letters on white paper.