Monotony is boring and tedious. Using a variety of methods makes it easier for students to concentrate during the entire class session because there aren’t any long, uninterrupted stretches of only listening. Experience has shown that students generally appreciate the use of a variety of methods.
Not all students do well with the same learning methods. By using a variety of methods, it is more likely that everyone will find their own way to make decent progress. Carefully individualized learning strategies allow students with a range of background knowledge to build up their knowledge and skills.
Certain methods may pose specific barriers or opportunities for certain students. For very reserved students or those with speech impairments, being asked to speak in front of the entire group can be very unpleasant. That might give you the impression, as the lecturer, that they are unprepared or performing poorly even though the same students could have made strong contributions to a smaller collaborative group. Others might have a very hard time spontaneously collaborating with classmates they do not know and would learn more by tackling the subject individually during or after the seminar. By using diverse methods, you will be helping improve equal opportunity.
A variety of methods also enables you to be creative, to try out new things, and to take conscious advantage of the results of various methods (such as highly focused silence or a lively atmosphere of discussion) in order to maintain suspense and interest throughout the semester. Your teaching and facilitation skills will improve as you learn from your experiences and expand your repertoire. You will add to your routine and be able to prepare for classes in less time. You will also discover what you are very good at and not as good at as a lecturer, which areas you might want to pursue in furthertraining, and where your personal strengths lie.