There are indeed reasons. They range from the absence of a reading culture among adult South Africans to the dearth of school libraries allied to the high cost of books and lastly to the low quality of training for teachers of reading.
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Some major causes of poor reading ability are difficult text, ADHD, dyslexia, limited vocabulary, working memory deficit, and more. People may also have trouble with comprehension due to boredom or disinterest in what they are reading.