Because computer-aided courses require the use of computers to teach, to understand lessons to students, but the teacher will uses computer will distract students not paying attention in class.
Because computer-aided programs require the use of computers to teach for students to be better able to understand the content of the class, but the teacher will allow students to use a computer that is not a distraction to concentrate in class.
Because the computer assisted curriculum needs to use the computer to teach, for students to understand the content of the class, but the teacher will feel that the use of computers will distract students from the class.