The fruitless search for the cause of the increase in illiteracy is a tragic example of file saying "They can't see the wood for the trees". When teachers use picture books, they are simply continuing a long-established tradition that is accepted without question. And for the past two decades, illustrations in reading primers have become increasingly detailed and obtrusive, while language has become impoverished -- sometimes to the point of extinction.
Amazingly, there is virtually no empirical evidence to support the use of illustrations in teaching reading. On the contrary, a great deal of empirical evidence shows that pictures interfere in a damaging way with all aspects of learning to read. Despite this, from North America to the Antipodes, the first books that many school children receive are totally without text.
A teacher's main concern is to help young beginning readers to develop not only the ability to recognize words, but the skills necessary to understand what these words mean. Even if a child is able to read aloud fluently, he or she may not be able to undersdand much of it: this is called "barking at text". The teacher's task of improving comprehension is made harder by influences outisde the classroom. But the adverse effects of such things as television, video games, or limited language experiences at home, can be offset by experiencing "rich" language at school.
Instead, it is not unusual for a book of 30 or more pages to have only one sentence full of repetitive phrases. The artwork is often marvellous, but the pictures make the language redundant, and the children have no need to imagine anything when they read such books. Looking at a picture actively prevents children younger than nine from creating a mental image, and can make it difficult for older children. In order to learn how to comprehend, they need to practise making their own meaning in response to text. They need to have their innate powers of imagination trained.
As they grow older, many children turn aside from books without pictures, and it is a situation made more serious as our culture becomes more visual. It is hard to wean children off picture books when pictures have played a major part throughout their formative reading experiences, and when there is competition for their attention from so many other sources of entertainment. The least intelligent are most vulnerable, but tests show that even intelligent children are being affected. The response of educators has been to extend use of pictures in books and to simplify the language, even at senior levels. The Universities of Oxford and Cambridge recently held joint conferences to discuss the noticeably rapid decline in literacy among their undergraduates.
Pictures are also used to help motivate children to read bacause they are beautiful and eyecatching. But motivation to read should be provided by listening to stories well read, where children imagine in response to the story. Then, as they start to read, they have this experience to help them understand the language. If we present pictures to save children the trouble of developing these creative skills, then I think we are making a great mistake.
Academic journals ranging from educational research, psychology, language learning, psycholinguistics, and so on c

A. they read too loudly
B. there are too many repetitive words
C. they are discouraged from using their imagination
D. they have difficulty assessing its meaning