Children who like workbooks feel this way because they are good at them, find them easy, and are not required to think critically. Many children want workbooks because they think they are supposed to have them. They see older students, older brothers and sisters, or neighborhood children using them. Children and parents like workbooks because they are perceptible evidence of something occurring in school (workbooks can often be the only tangible evidence of learning in the classroom). There are many more effective tangible items children can bring home.
Raising Readers: Helping Your Child to Literacy
by Steven Bialostok
(emphasis added by me!)