It is normally a mixture of manipulation and learning.
Generally in discussion, we listen to learn, and speak to manipulate. In a learning environment, we may spend a lot of time speaking, but only to manipulate someone into saying things which we can learn from. ('Could you repeat that', 'why is that do you suppose' and so on).
This may seem harsh to those who believe that conversations are about a mutual two way interaction, but even in a discussion, when we speak we are either