Cooperative learning is an effective approach in teaching busy classroom, why do some teachers avoid using it?

Cooperative learning can be effective if the number of students are limited in a classroom and are keen to study or gain knowledge but unfortunately these days teaching is more like profit oriented due to which the number of students per class is quite high in many schools and also the hunger of knowledge is dissappearing. Rather than looking into books students are busy with their mobile phones with their books open even in class rooms.