Literacy is one of Fallout GURPS advantages. See: Fallout GURPS.
The GM decides upon the norm for literacy in his campaign: Are most people literate, semi-literate or illiterate? Literacy is the norm in most high-tech settings, semi-literacy is usual in Renaissance and post-holocaust settings, and illiteracy is generally the default in lowtech and fantasy settings. Skip this section entirely in settings where there are no written languages!”— Steve Jackson Games GURPS sources
With the abandonment of GURPS, Literacy was recycled, image used for Intelligence.