Correcting dictation can lead to oral communication. Dictation can serve as an excellent review exercise. Dictation is psychologically powerful and challenging. Dictation fosters unconscious thinking in the new language. If the students do well, dictation is motivating.
Dictation involves the whole class, no matter how large it is.
During and after the dictation, all the students are active. Correction can be done by the students. Dictation can be prepared for mixed ability groups. Dictation can be prepared for any level. Dictation can be administered quite effectively by an inexperienced teacher.