You're asking yourself, "Uuuggghhh...Why do our teachers make us do presentations? That's a great question! The reason is that giving presentations helps build and strengthen a number of key skills that are necessary for success throughout life and career. Trust me, the reason is not to just torture you. It really is for your benefit. Let's explore further.
In order to be successful in any kind of work situation, you need to have solid communication skills. It doesn't matter what you do now for a job, or what you plan on doing years from now for your dream career, you need to know how to interact with others in verbal, written, and even non-verbal ways. You need to be able to express yourself in a clear, concise, professional, and friendly manner, and, at the same time, you need to be able to effectively listen to others in the forms of questions, feedback, and other important information being presented to you.
Giving presentations in front of your class, then, gives you crucial practice for these real-world situations that you will certainly come across repeatedly throughout your life. It doesn't matter if you're giving a presentation in your history class about World War II, or if you're talking about your favorite novel in front of your English class, or if you're discussing the atmosphere in your science class, the skills you're learning are the same - you're learning how to effectively and confidently communicate with others. These are valuable skills that will help you time and time again for the rest of your life.