Plagiarism is wrong for several reasons.
First, it is lying. If you have been asked to write something as evidence that you have grasped the materials of the course you are taking, offering someone else's work as evidence is a lie. It is no different from having someone else take an examination in your name.
Second, it is an insult to your fellow students. When you plagiarize, just as when you cheat on an exam, you treat unfairly those who play by the rules. You seek an unfair advantage over them, and inevitably, you will find yourself looking down on those who devote their time and energy to the task which you have cheated on.
Third, when you use other people words and ideas without their permission, it is stealing. It would be wrong to sneak into a factory and steal the products manufactured there during the day, and in the academy, words, ideas, paintings, compositions, sculpture, inventions, and other creations are what we produce. It is wrong to steal them and claim them as your own.
Plagiarism is a big deal in the