Bcz without classroom, there's no area of live competition and lectures of teachers help students keeping them on track.
The instructor helps his client through motivating him, and motivation is the key to start. Whenever we have to do something, most of us get distracted. That's the reason behind our failure. So whenever an instructor helps us, we feel motivated to study or work and have the courage that someone is there to help us. And we can start the process of work or study, if we fail, instructor again helps us, then maybe second time we can achieve our goals. At the end of the day, instructor's instructions instructs us to be on the right path of success which drives us leading a better and respectable life.
Classroom behavior management is something which is necessary to keep the students attentive to their study in classroom, being quiet and positive for learning.