because Lucas conceived the film as a retelling of the serials of his youth and wanted to give kids a modern fairy tale mythology and has been quoted many times as saying so . George Lucas in an interview in the New York Times, published on the 12th of September 1976:

It's for young people. 'Graffiti' was for 16-year-olds; this is for 14-year-olds. Young people don't have a fantasy life anymore, not the way we did. All they've got is Kojak and Dirty Harry. There's all these kids running around wanting to be killer cops.

https://archive.nytimes.com/www.nytimes.com/library/film/091276wars.html

and the drawings appear to YOU to show that , again , conjecture on your part and not fact .

See also…In the cover story of the April 1977 issue of American Film, for example, Lucas is quoted as saying: “I decided I wanted to make a children’s movie, to go the Disney route”; because he had realised that “a whole generation was growing up without fairytales” (Zito, 1977: 9, 13).