Large ccts because:
1. The instructor is too busy listening to his/her own voice and thinking the student needs to have some time to listen. Talk on the ground. Instruct in the air! Practice approach and landings when it's time to practice approach and landings. Practice straight and level away from the circuit. If you, as an instructor, have something important to say, make a full stop and talk on the taxi back to the threshold.
2. The student thinks he/she needs to have a long, stabilised approach for a good landing or he/she is just enjoying the view. What a waste of money!